Question

5. The sum of the digits of a two-digit number is 15.
When the digits are interchanged, the new number
is greater than the original number by 9. What is th
original number?​

Answer 1

AnswEr:-

Let the units digit be x and tens digit be y.

Then, x+y=15 ……….(i)

Given that,  10y+x

Interchanged digits: 10x+y

⇒(10x+y)−(10y+x)=9

⇒10x+y−10y−x=9

⇒9x−9y=9

⇒x−y=1 ………(ii)

Solving (i) and (ii)

x=8, y=7

∴ Two digit number=78.

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