Q. 133.8( 16 Votes )
The sum of the digits of a two - digit number is 15. The number obtained by interchanging the digits exceeds the given number by 9. Find the number.
Let the two - digit number be xy (i.e. 10x + y).
After interchanging the digits of the number xy, the new number becomes yx (i.e. 10y + x).
According to question -
x + y = 15.....(1)
(10y + x) - (10x + y) = 9
⇒ - 9x + 9y = 9
⇒ - x + y = 1.....(2)
Adding equations (1) and (2), we get -
y = 8
Substitute the value of y in equation (1), we get -
x = 7
Thus, the required number is 78.
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Solve the following pair of linear equation by cross - multiplication method:
x + 4y + 9 = 0
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