An Exercise on Rate, Ratio & Estimation | Direct & Inverse Proportion

Section A(1) & A(2) Practice

Question 1 MC
Simplify \( \frac{1}{3}:\frac{1}{4}:\frac{1}{5} \).
A. \( 3:4:5 \)     B. \( 4:3:5 \)     C. \( 20:15:12 \)     D. \( 12:15:20 \)

Question 2 MC
If \( y \) is directly proportional to \( x^2 \) and \( y = 8 \) when \( x = 2 \), find \( y \) when \( x = 4 \).
A. \( 16 \)     B. \( 24 \)     C. \( 32 \)     D. \( 64 \)

Question 3 Short Answer
If \( a:b = 3:4 \) and \( b:c = 5:6 \), find \( a:b:c \).

Question 4 Short Answer
Convert \( 90 \text{ km/h} \) to \( \text{m/s} \).

Question 5 MC
If \( y \) is inversely proportional to \( x \) and \( y = 12 \) when \( x = 5 \), find \( y \) when \( x = 15 \).
A. \( 4 \)     B. \( 6 \)     C. \( 18 \)     D. \( 36 \)

Question 6 Short Answer
Estimate \( \frac{61.2 \times 9.8}{3.02} \) by rounding to 1 significant figure.

Question 7 MC
Which of the following is a direct proportion?
A. \( y = 3x \)     B. \( y = \frac{3}{x} \)     C. \( y = 3x^2 \)     D. \( y = 3x + 1 \)

Question 8 Short Answer
Simplify \( 0.04:0.12:0.20 \).

Question 9 Short Answer
If \( 12 \) workers can build a wall in \( 6 \) days, how many days would it take \( 9 \) workers to build the same wall?

Question 10 Short Answer
The ratio of boys to girls in a class is \( 3:2 \). If there are \( 30 \) students in total, how many boys are there?