Question

6 identical coins are arranged in a row, the no. of ways in which the no. of tails is equal to the no. of heads is?

Answer 1

For equal number of heads and tails it is easily understood that three heads will have to accompany three tails.

Out of 6 coins, 3 heads can be obtained in ⁶C₃ ways
So, ⁶C₃ = 6!/3!3! => (6 x 5 x 4 x 3 x 2 x 1)/(3 x 2 x 1)(3 x 2 x 1)

=> (6 x 5 x 4)/(3 x 2 x 1)

=> 5 x 4 = 20