HHHH HHHT HHTH HHTT HTHH HTHT HTTH HTTT THHH THHT THTH THTT TTHH TTHT TTTH TTTT

There are 16 ways the tosses can come out. The ways for which there are two heads and two tails are HHTT, HTHT, HTTH, THHT, THTH, and TTHH. Since each way has the same probablity (namely 1/2 x 1/2 x 1/2 x 1/2 = 1/16), the chance that the four tosses result in two heads and two tails is 6/16 = 3/8 = .375, or 37.5%. (38.29% is what you get if you use the normal curve method of approximating the chance.) ! !I