Q. 25.0( 6 Votes )

# By cross multipli

Answer :

Let the required two digit number be (10x + y) where x is the digit at tens place and y is the digit at unit place.

On interchanging the digits the two digit number formed will be (10y + x).

According to the question,

y = 2x and (10y + x) = 36 + (10x + y)

⇒ 2x – y = 0 and 10x + y – 10 y – x + 36 = 0

⇒ 2x –y = 0 and 9x – 9y + 36 = 0

⇒ 2x – y = 0 and x – y + 4 = 0

On comparing with a_{1}x + b_{1}y + c_{1} = 0 and a_{2}x + b_{2}y + c_{2} = 0we get,

a_{1 =} 2, b_{1} = – 1, c_{1} = 0; a_{2} = 1, b_{2} = – 1, c_{2} = 4

Applying cross multiplication method which says,

Putting the given values in the above equation we get,

Similarly,

∴The solution of the pair of equations is (4, 8).

So, the required two digit number will be (10x + y) = (10× 4 + 8) = 48

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