Children at the party.
Algebra
Level
2
Each child of a group gives a gift to other children. Total number of gifts are 110. Then find the number of children in the group.
The answer is 11.
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Let there be n children. 1st gives to remaining ( n - 1), and receives also from (n - 1). 2nd gives to remaining (n-2) and receives also from them. . . . ....1 and 1. The sum is 2( n - 1)n/2. But this is = 110
n 2 − n − 1 1 0 = ( n − 1 1 ) ( n + 1 0 ) ⟹ n = 1 1 .