A number consists of rwo digit number whose sum is 9. If9 is subtracted from the number its digits are interchanged. Find the number

Answer 1

Your number = 10 a + b

a + b = 9

If 9 is subtracted from the number its digits are interchanged mean:

10 a + b - 9 = 10 b + a

Now:

10 a - 9 - a = 10 b - b

9 a - 9 = 9 b Divide both sides by 9

a - 1 = b

You must solve system:

a + b = 9

a - 1 = b

Try that.

The solutions are:

a = 5 , b = 4

Your number = 10 a + b = 10 ∙ 5 + 4 = 50 + 4 = 54

Proof:

5 + 4 = 9

54 - 9 = 45