Question

the total no. of ways of selecting six coins out of 20 one rupee coins, 10 fifty paise coins and 7 twenty five paise coins is
a)28
b)56
c)37C6
d)none of these

Answer 1

answer for this question is option c

Answer 2

Given, n = 3(20 one rupee coins, 10 fifty paise coins, 7 twenty-five paise)
             r = 6
 The formula is: n + r - 1 Cr

                             = 3 + 6 - 1 C6

                             = 8C6  (nCr = n!/r! * (n-r)!)

                             = 8!/6! * (8-6)!

                             = 8 * 7* 6 * 5 * 4 * 3 * 2 * 1/(6 * 5 * 4 * 3 * 2 * 1) * (2 * 1)

                             = 28.

Hope this helps!