The ones digit of a number is 3 times the tens digit. If the digits are reversed, the new number is 18 more than the original number. Find the original number.

Question

Can you give me the answer?

Answer 1

Remember that the decimal number system is a positional number system.

For a number that looks like ab, the value is 10a+b.

The original number is (10a+b); the reversed number is (10b+a). They differ by 18.

10b+a = (10a+b) + 18

b is 3 times a

b = 3a

Substitute:

10(3a) + a = 10a + 3a + 18

31a = 13a + 18

18a = 19

a = 1

so b = 3 (3 times a)

The original number is 13; the reversed number is 31; the reversed number is 18 more than the original.

Answer 2

let the number be xy

y = 3x

yx = xy + 18

so, x could be 0, 1, 2, 3

If x = 0, then y = 0, so that's not it

if x = 1, then y = 3, so that's 31

31 - 18 = 13

31 and 13 are the answer