In tossing 10 coins the probability of getting exactly 5 heads is?

252/1024 or 0.246.

One method of calculating it is this: The total number of outcomes possible by tossing a coin 10 times is 2 to the 10th, which is 1024. In addition, getting 5 heads in 10 tosses is like arranging 5 identical objects in 10 spaces (the remaining 5 spaces are by default Tails), which can be done in 10C5 ways, which is 252. So the probability of getting 5 heads is 252/1024.