Question

(5+5) + (5 + 6) + (5 + 7) + (5 + 8) + .... + (5 + 14) + (5 + 15)

(11 times 10) + what number?
A, 15
B, 50
C, 55
D, 99
​

Answer 1

C: 55

Explanation:

Rearrange the bracketed terms to:

(10 + 0) + (10 + 1) + (10 + 2) + ... + (10 + 10)

There are 11 brackets so we have (11 * 10) + (0 + 1 + 2 + ... + 10) =

(11 * 10) + 55