If 30% of A = 0.25 of B = 0.2 of C, then find A : B : C?

The correct answer is Option (2) → 10 : 12 : 15

When three quantities are equal, set each equal to one common value \(k\) and write A, B and C in terms of \(k\); 30% of A is \(0.3A\).

• The common value: \(0.3A=0.25B=0.2C=k\)

• A in terms of \(k\): \(\displaystyle A=\frac{k}{0.3}=\frac{10k}{3}\)

• B in terms of \(k\): \(\displaystyle B=\frac{k}{0.25}=4k\)

• C in terms of \(k\): \(\displaystyle C=\frac{k}{0.2}=5k\)

• The ratio, with \(k\) cancelling: \(\displaystyle A:B:C=\frac{10}{3}:4:5=10:12:15\) (all terms multiplied by 3 to clear the fraction)