CAT 2020 Slot 2QA Question 7

RatioEasy

A sum of money is split among Amal, Sunil and Mita so that the ratio of the shares of Amal and Sunil is 3 : 2, while the ratio of the shares of Sunil and Mita is 4 : 5. If the difference between the largest and the smallest of these three shares is Rs 400, then Sunil’s share, in rupees, is

Answer & solution

Answer: 800

Solution

Easy

Combine the two pairwise ratios into a single three-way ratio by making Sunil's part common, then translate "difference of largest and smallest = 400" into one equation for the scale factor.

1

Merge the ratios. Amal : Sunil =3:2=3:2 and Sunil : Mita =4:5=4:5. Scale the first by 22 so Sunil matches.

A:S=3:2=6:4S:M=4:5 A:S:M=6:4:5\begin{aligned} &A:S = 3:2 = 6:4\\ &S:M = 4:5\\ &\Rightarrow\ A:S:M = 6:4:5 \end{aligned}
2

Use the difference. Let the parts be 6x,4x,5x6x,4x,5x. Largest is Amal (6x6x), smallest is Sunil (4x4x).

6x4x=400 2x=400 x=200\begin{aligned} &6x - 4x = 400\\ &\Rightarrow\ 2x = 400\\ &\Rightarrow\ x = 200 \end{aligned}
3

Sunil's share. Sunil's part is 4x4x.

4x=4×200=8004x = 4\times 200 = 800
Sunil’s share=Rs 800\text{Sunil's share} = \text{Rs }800