Question

On the independence day, in a group of children, each children gives one gift to the other. If total number of gifts are 90, then find the number of children in the group.

Note : I am not sure whether this question is of AP or quadratic, still I am posting it in AP section.

Answer 1

take n be child no.. so that n(n-1)=90 n^2-n=90 when u solve this you will get n-10=0 and n+9=0 hence n=10 since every child have to give gift to other excluding himself so n-1.. hence n =10