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Re: 6 balls are marked with numbers 1 to 6. If two balls are picked out [#permalink]
Carcass, can you please explain why you multiplied by 5 here? What this formula is?
6 balls and two picked up So the total ways are

6*5/2=15
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6 balls are marked with numbers 1 to 6. If two balls are picked out [#permalink]
Expert Reply
If you pick up 2 among 6 then is a combinatorics formula

\(\dfrac{6*5*4*3*2*1}{2*4*3*2*1}\)

\(4*3*2*1\) cancel out and we laft with

\(\dfrac{6*5}{2}\)

I hope now more clear

See here for more

Permutation & Combination
PERMUTATIONS and COMBINATIONS Simplified
Combinatorics: An Intuitive Approach
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6 balls are marked with numbers 1 to 6. If two balls are picked out [#permalink]
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