Assuming the weight condition implies, "the probability of obtaining a head is 2 1/2 times that of obtaining a tail," what is the probability of obtaining a head?
An "unfair" coin has a Heads side which weighs two-and-a-half times heavier than the Tails side.
If you toss this unfair coin 100 times, how many of those times would you expect to see Heads?
The Heads side is times heavier than the Tails side.
The Heads side will be on the bottom of the time.
We expect to see Heads: . times.