2002 AMC 12B Problems/Problem 10

Problem

How many different integers can be expressed as the sum of three distinct members of the set ?

Solution

We can make all multiples of three between 1+4+7=12 and 13+16+19=48, inclusive. There are $\frac{48}{3}-\frac{12}{3}+1=13\Rightarrow \boxed{\mathrm{(A)}$ (Error compiling LaTeX. Unknown error_msg) integers we can form.