UPSC CDS 1 2021 Math Paper

Ratio of incomes of A:B:C=7:9:12
Ratio of spending of A:B:C=8:9:15
Let incomes of A,B‌&C=7x,9x‌&12x respectively
Let spending of A,B‌&C=8v,9y‌&15y respectively
According to the question,
7x8y=‌

1

4

×7x⇒7x−‌

7x

4

=8y
‌

21x

4

=8y→‌

x

y

=‌

32

21

Saving of A=7×32−8×21=56
Saving of B =9×329×21=99
Saving of C=12×32−15×21=69
Ratio of saving of A:B:C=56:99:69