The difference between the digits in a two-digit number is 3. The units' digit is twice the tens' digit. Find the numeral.

Question

Let t= tens' digit

Let u= units' digit

Answer 1

Let x = tens digit and y = ones digit

Then, y = 2x (so y is larger than x) and y - x = 3

So, x + 3 = 2x

x = 3 and y = 6

The number is 36

Answer 2

Starting off, the question asks us to find a two-digit number, tu, satisfying two conditions.

1. The difference between the digits is 3
2. u is twice of t

If we list out all possibilities for #2, we get the list {12, 24, 36, 48}. No other two-digit numbers satisfy this condition (since 00 isn't technically a two-digit number). Using this list, we can then find the differences and see that the only number satisfying our conditions is 36.