53. 7 + 14+ ... 77

FYI - one other way you can do this problem is to realize that the problem may also be expressed as:

7*(1 + 2 + ... + 11) which equals 7*[(11)*(11+1)/2] (formula for sum of first consecutive n numbers) = 7*11*6=42*11=462.

For me this one comes to mind more quickly, and it never hurts to have more than one option available under the time pressures during the test.