RRB Group D Model Paper 2 with solutions

Question : 79 of 100

Marks: +1, -0

If A and B are in the ratio 4 : 5 and the difference of their squares is 81, then the value of A is_________.

Solution:

(4) Let A = 4n and B = 5n
According to the question:

(5n)^2 – (4n)^2

= 81
⇒ 25

n^2

– 16

n^2

= 81
⇒ 9

n^2

= 81
⇒

n^2

= 9
⇒ n = 3
∴ A = 4n = 12

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