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Mathematics 7 Online
OpenStudy (anonymous):

If n is a positive integer, how does the number of combinations for nCn-1 compare to the number of combinations for nC1?

ganeshie8 (ganeshie8):

hint : number of ways of choosing 1 object = number of ways of leaving one object

ganeshie8 (ganeshie8):

does that help ha

OpenStudy (anonymous):

lol yes it did :)

ganeshie8 (ganeshie8):

suppose, u have 4 shirts, and u want to choose one shirt : how many ways u can choose ?

ganeshie8 (ganeshie8):

from 4 shirts, u can choose 1 shirt in 4c1 = 4 ways

ganeshie8 (ganeshie8):

next, if u want to LEAVE 1 shirt and choose 3 shirts, then ho many ways u wud get ? from 4 shirts, u can LEAVE 1 shirt in 4c3 = 4 ways

ganeshie8 (ganeshie8):

leaving 1 shirt is same as choosing 3 shirts

ganeshie8 (ganeshie8):

i mean, if you're choosing 3 shirts --- then that means you're leaving behind 1 shirt

ganeshie8 (ganeshie8):

so, in general : \(\large ^nC_r = ^nC_{n-r}\)

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