Question

the sum of the digits of a two digit number is 15 the number obtained by interchanging its digits exceeds the given number by 9 find the original number

Answer 1

let the digit at unit place to be x
then digit at tens place =15-x
so original no.=10(15-x)+x
=150-10x+x
=150-9x

if digit get interchange then;
digit at once place=(15-x)
and at tens place=x
so new no.=10(x)+15-x
=10x+15-x
=9x+15

so the no. is : original no -new no.=9
150-9x -(9x+15)=9
150-9x-9x-15=9
135-18x=9
-18x=-135+9
-18x=-126
x=7


so digit at unit place is 7 and at tens place is 8 so the digit formed is 87