A two digit number is four times the sum of its digits. The tens digit is 3 less that the units digit. What is the number?

Question

A two digit number is four times the sum of its digits. The tens digit is 3 less that the units digit. What is the number?

Answer 1

The trick with this problem is to remember that the number is 10t + u.

 

4(t + u) = 10t + u

t = u -3

 

Multiply and collect terms in the 1st equation to get 3u = 6t

 

Substitute from the 2nd equation: 3u = 6(u-3)

 

Multiply and collect terms to get: 3u = 18

 

u=6, then t=3

 

and sure enough 36 = (6+3)*4