When six fair coins are tossed simultaneously, in how many of the outcomes will at most three of the coins turn up as heads?
Total number of coins =6
(1) '0' heads =1 chance(6C0)
(2) '1' heads =6 chance(6C1)
(3) '2' heads=15 chance(6C2)
(4) '3' heads=20 chance (6C3)
Hence total outcome =42