   SEARCH HOME Math Central Quandaries & Queries  Question from Madison, a student: Trini took some photos. The number of photos she took is a two digit number. The sum of the digits is 11. The tens digit is 3 more than the ones digit. How many photos did Trini take? The smallest the ones digit can be is 0 and since the tens digit is 3 more than the units digit, the number might be 30. Likewise if the ones digit is 1 then the tens digit is 1 + 3 = 4 so the number might be 41. Continue this way and write down all the possibilities, there are only seven. For which of the numbers you wrote down is the sum of the digits 11?

I think however that you are expected to use algebra to solve this problem. In this case let the tens digit be $t$ and the ones digit, units digit, be $u.$ The sum of the digits is $11$ so

$t + u = 11$

The tens digit is 3 more than the ones digit. Write this an an equation is $t$ and $u.$ Solve the two equations for $t$ and $u.$

Penny      Math Central is supported by the University of Regina and the Imperial Oil Foundation.