Question

the sum of the two digits is 9. if 63 is subtracted from the no. its digits are reversed find the no.

Answer 1

Answer:

Number obtained by reversing the digits = 10 (9 - x) + x = 90 - 9x. =>x = 8. So, ten's digit = 8 and unit's digit = 1. Hence, the required number is 81.

Answer 2

Answer:

Let x and y be the digits

x+y=9 ------(1)

10x+y-63=10y+x

9x-9y=63

Dividing by 9

x-y=7 -------(2)

Now (1) + (2)

x+y=9

x-y=7

----------

2x=16

x=8

Now substituting x=8 in (1)

8+y=9

y=1

Thus the number is 81

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