When 4 fair coins are tossed together what is the probability of getting at least 3 heads?

When 4 fair coins are tossed simultaneously, the total number of outcomes is 2⁴ = 16
At least 3 heads imply that one can get either 3 heads or 4 heads.
One can get 3 heads in ⁴C₃ = 4 ways and can get 4 heads in ⁴C₄

∴ Total number of favorable outcomes = 4 + 1 = 5
∴ The required probability = 1/4.

[To get 3 heads, means that one gets only one tail. This tail can be either the 1st coin, the 2nd coin, the 3rd, or the 4th coin. Thus there are only 4 outcomes which have three heads. The probability is 4/16 = 1/4.]