What least fraction should be added to
1/(2 × 3) + 1/(3 × 4) + 1/(4 × 5) + ....... + 1/(21 × 22)
so that the result is unity?	Answers:
A) 5/11 B) 6/11 C) 4/11 D) 7/11 E) 8/11
Explanation:   Given expression   = 1/(2 × 3) + 1/(3 × 4) + 1/(4 × 5) + ...... + 1/(21 × 22)   = (1/2 - 1/3) + (1/3 - 1/4) + (1/4 - 1/5) + ..........   = (1/21 - 1/22) = 1/2 - 1/22 = 10/22 = 5/11   Thus, least fraction to be added = 1 - 5/11 = 6/11   Answer: Option 6/11
<result>B</result>
What least fraction should be added to
1/(2 × 3) + 1/(3 × 4) + 1/(4 × 5) + ....... + 1/(21 × 22)
so that the result is unity?