for an international mathematics olympiad , country d will send 6 delegates in total — two will be supervisors and 4 will be contestants . there are 210 ways in which the 6 delegates can be chosen and there are 7 candidates competing for the 4 contestants ’ places available . how many candidates are competing for the two supervisors ’ slots available ?
Choose the correct option.
A) 1  B) 2  C) 3  D) 4  E) 5

Rationale: option a wrong as 2 supervisor need to be selected . going by statement : 4 contestant chosen from 7 - - 7 c 4 = = 35 and total ways = 210 consider 2 supervisor will be chosen from : x people . so as per question : 35 * x = 210 x = 6 so by using options , option a already decided wrong . option b 2 c 2 will be 1 not 6 . option c 3 c 2 will be 3 not 6 option d 4 c 2 will be 6 correct answer option e 5 c 2 will be 10 not 6 . ans : d
Answer: D