1.

The sum of the digits of a two digit number is 6, if 9 is subtracted from 4 times the number, the digits will interchanged. What is the number?1. 512. 123. 154. 815. 21

Answer» Correct Answer - Option 3 : 15

Solution:

Let the number be xy = 10x + y

And reverse of a number is yx = 10y + x

According to the question, x + y = 6      ----(1)

Also if 9 is subtracted from 4 times the number, the digits will interchanged.

⇒ 4(10x + y) – 9 = 10y + x

⇒ 40x + 4y -9 = 10y + x

⇒ 39x – 6y = 9      ----(2)

On solving equation (1) and (2)

⇒ x = 1 and y = 5

Hence the number is 15.


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