Mathematics 10 — Exercise 11.1 · Q1 (i–ii)
Full question
The table gives the scores in a memory test, in classes 44–48, 49–53, 54–58, 59–63, 64–68, 69–73 and 74–78. Draw a cumulative-frequency graph. Use it to estimate the median, first and third quartiles Q₁ and Q₃, third decile D₃, 90th percentile P₉₀ and interquartile range. Give answers to the nearest whole number.
| Score interval | Frequency |
|---|---|
| 44–48 | 3 |
| 49–53 | 12 |
| 54–58 | 15 |
| 59–63 | 23 |
| 64–68 | 12 |
| 69–73 | 8 |
| 74–78 | 7 |
Step-by-step solution
The scores are whole numbers. Convert each interval to continuous boundaries by subtracting 0.5 from its lower limit and adding 0.5 to its upper limit:44–48 becomes 43.5–48.5,49–53 becomes 48.5–53.5, and so on.
Cumulative frequency means a running total. Begin with zero at the first lower boundary.
Class 87/2–97/2: add frequency 3 to the preceding total.
Class 97/2–107/2: add frequency 12 to the preceding total.
Class 107/2–117/2: add frequency 15 to the preceding total.
Class 117/2–127/2: add frequency 23 to the preceding total.
Class 127/2–137/2: add frequency 12 to the preceding total.
Class 137/2–147/2: add frequency 8 to the preceding total.
Class 147/2–157/2: add frequency 7 to the preceding total.
Plot each UPPER boundary against its cumulative frequency, and join adjacent points.
Median: find the cumulative-frequency position 1/2×80.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Calculate this operation before combining the remaining terms.
Keep the common denominator and add the signed numerators.
Calculate this operation before combining the remaining terms.
Median lies between cumulative totals 30 and 53. Interpolate along that graph segment: lower boundary + (position−previous total)/class frequency × class width.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Calculate this operation before combining the remaining terms.
To add these fractions, first use a common denominator: the least common multiple of their denominators.
Multiply this numerator AND denominator by the same factor. Its value stays unchanged.
Calculate the converted numerator; the denominator is now common.
Multiply this numerator AND denominator by the same factor. Its value stays unchanged.
Calculate the converted numerator; the denominator is now common.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Calculate this operation before combining the remaining terms.
Keep the common denominator and add the signed numerators.
Calculate this operation before combining the remaining terms.
Median ≈ 60.674, rounded to a whole number: 61.
Q1: find the cumulative-frequency position 1/4×80.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate this operation before combining the remaining terms.
Keep the common denominator and add the signed numerators.
Calculate this operation before combining the remaining terms.
Q1 lies between cumulative totals 15 and 30. Interpolate along that graph segment: lower boundary + (position−previous total)/class frequency × class width.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
The numerator and denominator have this greatest common divisor. Divide BOTH by it.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Show the two divisions explicitly.
Write the reduced fraction.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate this operation before combining the remaining terms.
Show the two divisions explicitly.
Evaluate the numerator division.
Evaluate the denominator division.
Write the reduced fraction.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Calculate this operation before combining the remaining terms.
To add these fractions, first use a common denominator: the least common multiple of their denominators.
Multiply this numerator AND denominator by the same factor. Its value stays unchanged.
Calculate the converted numerator; the denominator is now common.
Multiply this numerator AND denominator by the same factor. Its value stays unchanged.
Calculate the converted numerator; the denominator is now common.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Calculate this operation before combining the remaining terms.
Keep the common denominator and add the signed numerators.
Calculate this operation before combining the remaining terms.
Q1 ≈ 55.167, rounded to a whole number: 55.
Q3: find the cumulative-frequency position 3/4×80.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Calculate this operation before combining the remaining terms.
Keep the common denominator and add the signed numerators.
Calculate this operation before combining the remaining terms.
Q3 lies between cumulative totals 53 and 65. Interpolate along that graph segment: lower boundary + (position−previous total)/class frequency × class width.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Calculate this operation before combining the remaining terms.
To add these fractions, first use a common denominator: the least common multiple of their denominators.
Multiply this numerator AND denominator by the same factor. Its value stays unchanged.
Calculate the converted numerator; the denominator is now common.
Multiply this numerator AND denominator by the same factor. Its value stays unchanged.
Calculate the converted numerator; the denominator is now common.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate this operation before combining the remaining terms.
Keep the common denominator and add the signed numerators.
Calculate this operation before combining the remaining terms.
Q3 ≈ 66.417, rounded to a whole number: 66.
D3: find the cumulative-frequency position 3/10×80.
Keep the common denominator and add the signed numerators.
Calculate this operation before combining the remaining terms.
D3 lies between cumulative totals 15 and 30. Interpolate along that graph segment: lower boundary + (position−previous total)/class frequency × class width.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
The numerator and denominator have this greatest common divisor. Divide BOTH by it.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Show the two divisions explicitly.
Evaluate the denominator division.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Show the two divisions explicitly.
Write the reduced fraction.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate this operation before combining the remaining terms.
Show the two divisions explicitly.
Evaluate the numerator division.
Evaluate the denominator division.
Write the reduced fraction.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
The numerator and denominator have this greatest common divisor. Divide BOTH by it.
Calculate this operation before combining the remaining terms.
Show the two divisions explicitly.
Evaluate the numerator division.
Evaluate the denominator division.
Write the reduced fraction.
Calculate this operation before combining the remaining terms.
To add these fractions, first use a common denominator: the least common multiple of their denominators.
Multiply this numerator AND denominator by the same factor. Its value stays unchanged.
Calculate the converted numerator; the denominator is now common.
Multiply this numerator AND denominator by the same factor. Its value stays unchanged.
Calculate the converted numerator; the denominator is now common.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Calculate this operation before combining the remaining terms.
Keep the common denominator and add the signed numerators.
Calculate this operation before combining the remaining terms.
D3 ≈ 56.500, rounded to a whole number: 57.
P90: find the cumulative-frequency position 9/10×80.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Calculate this operation before combining the remaining terms.
Keep the common denominator and add the signed numerators.
Calculate this operation before combining the remaining terms.
P90 lies between cumulative totals 65 and 73. Interpolate along that graph segment: lower boundary + (position−previous total)/class frequency × class width.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Calculate this operation before combining the remaining terms.
To add these fractions, first use a common denominator: the least common multiple of their denominators.
Multiply this numerator AND denominator by the same factor. Its value stays unchanged.
Calculate the converted numerator; the denominator is now common.
Multiply this numerator AND denominator by the same factor. Its value stays unchanged.
Calculate the converted numerator; the denominator is now common.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Calculate this operation before combining the remaining terms.
Keep the common denominator and add the signed numerators.
Calculate this operation before combining the remaining terms.
P90 ≈ 72.875, rounded to a whole number: 73.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Calculate this operation before combining the remaining terms.
Interquartile range is Q3−Q1.
To add these fractions, first use a common denominator: the least common multiple of their denominators.
Multiply this numerator AND denominator by the same factor. Its value stays unchanged.
Calculate the converted numerator; the denominator is now common.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate this operation before combining the remaining terms.
Multiply this numerator AND denominator by the same factor. Its value stays unchanged.
For multiplication of fractions, multiply the numerators together and the denominators together.
The numerator and denominator have this greatest common divisor. Divide BOTH by it.
Show the two divisions explicitly.
Evaluate the numerator division.
Evaluate the denominator division.
Calculate this operation before combining the remaining terms.
Calculate the converted numerator; the denominator is now common.
Calculate this operation before combining the remaining terms.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Calculate this operation before combining the remaining terms.
Keep the common denominator and add the signed numerators.
The numerator and denominator have this greatest common divisor. Divide BOTH by it.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Show the two divisions explicitly.
Write the reduced fraction.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate these two products separately.
Show the two divisions explicitly.
Write the reduced fraction.
Calculate this operation before combining the remaining terms.
For multiplication of fractions, multiply the numerators together and the denominators together.
Calculate this operation before combining the remaining terms.
Show the two divisions explicitly.
Evaluate the numerator division.
Evaluate the denominator division.
Write the reduced fraction.
Calculate this operation before combining the remaining terms.
| Class | f | Cumulative f |
|---|---|---|
| 43.5–48.5 | 3 | 3 |
| 48.5–53.5 | 12 | 15 |
| 53.5–58.5 | 15 | 30 |
| 58.5–63.5 | 23 | 53 |
| 63.5–68.5 | 12 | 65 |
| 68.5–73.5 | 8 | 73 |
| 73.5–78.5 | 7 | 80 |
Answer
Median ≈ 61; Q1 ≈ 55; Q3 ≈ 66; D3 ≈ 57; P90 ≈ 73; IQR ≈ 11