CAT 1996 — QA Question 28

This can simply be solved by multiplying the two multiplication factors to get the effective multiplication factor. e.g. multiplication factor for 30% increase = 1.30. Multiplication factor for 20% decrease = 0.8. Hence, 1.30 × 0.8 = 1.04. This multiplication factor (i.e. 1.04) indicates that there is a 4% increase in total revenue. So the answer is +4.

Alternative method:
By using the formula x + y + $\frac{xy}{100}$

∴ x = +30%; y = – 20%

⇒ 30 + 60 + $\frac{50(-20)}{100}$

= 30 – 20 – 6 = +4%