<PRE><B>Question 549504</B>
After tossing some coins, it is observed that the probability of obtaining 10 heads and 15 tails 
is the same as the probability of obtaining 15 heads and 10 tails. 
Find the least number of coins tossed
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P(10 h and 15 t) = nC10(1/2)^n
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P(15 h and 10 t) = nC15(1/2)^n
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nC10 = nC15
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n!/(n-15)!*15! = n!/(n-10)!*10!
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(n-15)!*15! = (n-10)!*10!
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(n-15)!*15*14*13*12*11 = (n-10)!
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15*14*13*12*11 = (n-10)(n-11)(n-12)(n-13)(n-14)
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So n-10 = 15
n = 25
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Cheers,
Stan H.
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