Which fraction should be added to:
1/(2 Ã— 3) + 1/(3 Ã— 4) + 1/(4 Ã— 5) + ....... + 1/(27 Ã— 28)
so that the result is equal to 1?  Choices:
A) 11/28
B) 13/28
C) 15/28
D) 17/28
E) 19/28
The given expression   = 1/(2 Ã— 3) + 1/(3 Ã— 4) + 1/(4 Ã— 5) + ...... + 1/(27 Ã— 28)   = (1/2 - 1/3) + (1/3 - 1/4) + (1/4 - 1/5) + .......... + (1/27 - 1/28)   = 1/2 - 1/28 = 13/28   Thus, the fraction we should add = 1 - 13/28 = 15/28   The answer is 15/28.
<result>C</result>
Which fraction should be added to:
1/(2 Ã— 3) + 1/(3 Ã— 4) + 1/(4 Ã— 5) + ....... + 1/(27 Ã— 28)
so that the result is equal to 1?