In a society for children, each child gives gift to every other child. If the total number of gifts is 132, find the number of children.

Asked by godson babuji | 15th Mar, 2015, 02:24: AM

Expert Answer:

L e t space t h e space n u m b e r space o f space c h i l d r e n space b e space apostrophe n apostrophe 2 cross times to the power of n C subscript 2 equals 132 rightwards double arrow 2 cross times fraction numerator n left parenthesis n minus 1 right parenthesis over denominator 2 end fraction equals 132 rightwards double arrow n squared minus n minus 132 equals 0 rightwards double arrow n squared minus 12 n plus 11 n minus 132 equals 0 rightwards double arrow n left parenthesis n minus 12 right parenthesis plus 11 left parenthesis n minus 12 right parenthesis equals 0 rightwards double arrow left parenthesis n minus 12 right parenthesis left parenthesis n plus 11 right parenthesis equals 0 therefore n equals 12 space N u m b e r space o f space c h i l d r e n space i s space 12.

Answered by Prasenjit Paul | 15th Mar, 2015, 09:31: AM

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