Question

Sum of two digit number is9.When we interchange the digits it is found that the resulting new number becomes twice the other number. What are the numbers

Answer 1

4 and 5

Explanation:

Let the numbers be x and y

If their sum is 9, hence;

x + y = 9 ....1

When reversed

10y+x = 2(10x+y)

10y+x = 20x + 2y

10y - 2y = 20x - x

8y = 19x

y = 10x/8 ...2

Substitute equation 2 into 1;

From 1;

x+y = 9

x +(10x/8) = 9

18x/8 = 9

18x = 72

x = 72/18

x = 4

Since x+y =9

y = 9-x

y =9-4

y = 5

Hence the numbers are 4 and 5