8. If a:b=c:d then prove that
(a) (5a +7b)(5c -7 d) = (5a - 7b)(50 +7 d)
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Sum of the digits of a two-digit number is 12. The given number exceeds the number obtained by interchanging the digits by 36. Find the given
number.
The tens digit of the required number be x
and the units digit be y
x + y = 12 ......... eq. (1)
Required number = (10x + y)
Number obtained on reversing the digits = (10y + x)
(10y + x) - (10x + y) = 18
9y - 9x = 18
x - y = 12 ......... eq. (2)<br>
On adding eq. (1) and eq. (2)
x + y + y - x = 12 +2
2y = 14
y = 2
x = 5
Hence, the required number is 57
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