The length of 3 ropes are in the ratio 4 : 5 : 6. If the sum of the weights of the longest and the shortest rope is 100 metres more than the length of the third rope, what is the length of the shortest rope?
Answers:	A) 80 m	B) 180 m	C) 100 m	D) 60 m	E) of these

Rationale: let the lengths of the three ropes be 4 k , 5 k and 6 k respectively . 4 k + 6 k = 5 k + 100 = > 5 k = 100 = > k = 20 therefore the weight of the lightest boy = 4 k = 4 ( 20 ) = 80 m answer : a
Answer: A