Absolute Frequency and Relative Frequency

All five frequencies must add up to the class total of 25 students.

The four known frequencies add to $2+6+7+1=16$.

So the missing Satisfactory frequency is $25-16=9$ students. Checking: $2+6+9+7+1=25$.

A relative frequency of $40\%$ means 40 out of every 100, which as a decimal is $0.4$.

To turn a relative frequency into an absolute frequency, multiply by the total count: $0.4\times 50=20$.

So 20 students chose Sports. As a check, the four activities give $15+20+10+5=50$ students.

First turn each relative frequency into an absolute frequency by multiplying by the total of 80 students.

Bus: $0.4\times 80=32$ students. Cycle: $0.1\times 80=8$ students.

"How many more" means subtract: $32-8=24$ students. Note that the answer must be a number of students, not a difference in percentages.

First find the total number of customers: $50+80+20=150$.

Cash was used by 50 of them, so the cash fraction is $\frac{50}{150}=\frac{1}{3}$.

A full pie chart is $360°$, so the cash sector is $\frac{1}{3}\times 360°=120°$.

The frequencies add to $18+12+15+15=60$, which matches the class size.

Relative frequency of bananas: $\frac{12}{60}=0.2=20\%$.

A full pie chart is $360°$, so the banana sector is $0.2\times 360°=72°$.

The Milk sector is labelled $20\%$ of the chart, which as a decimal is $0.2$.

Number of students: $0.2\times 90=18$ students.

Angle: a full pie chart is $360°$, so the Milk sector is $0.2\times 360°=72°$. The angle depends only on the percentage, while the number of students depends on the total of 90.