Question

A 3 kg bag of rice lasts exactly 30 days for Mrs. and Mr. Pestonjee when both consume equal amounts. If Mr. Pestonjee cuts down his rice intake by half on his doctor's advice, how many days would a 3 kg bag last them? A 35 B 40 C 42 D 45

Answer 1

40

Explanation:

they both consume equal amounts.

let's call his intake M and hers F.

1.5M + 1.5F = 3(kg)

if he reduces his intake by half, he now only has 1.5/2 = 0.75 in exactly 30 days.

their collective intake is now 0.75M + 1.5F

1.5 + 0.75 = 2.25.

3/2.25 = 4/3.

4/3 is one third more than 3/3 (1).

so a 3kg bag will last one third longer than 30 days. 30 X 4/3 = 120/3 = 40 (days).