1. A coin is tossed four times. What is the probability of getting four heads?
Each toss has a 1/2 chance of getting a head.
So the chance of getting all four heads can be calculated as :
2. A coin is tossed four times. What is the probability of getting two heads?
Each toss can have 2 results, so 4 flips will have or 16 results.
Getting two heads means getting two tails also. So, we can get the number of times two heads come = = 6
We can write the groups like - {HHTT,HTHT,HTTH,THHT,THTH,TTHH}
So, the required probability is : 6/16 or 3/8.
3. Not getting two heads means getting 3 tails and 1 head or all tails.
Probability of having all tails =
Probability of one head(1st trial) and three tails = 1/16
Probability of one head (2nd trial) and three tails (the 1st, 3rd and 4th trials) = 1/16
Probability of one head (3rd trial) and three tails (the 1st, 2nd and 4th trials) = 1/16
Probability of one head (4th trial) and three tails (the 1st, 2nd and 3rd trials) = 1/16
So, the total probability showing only one or none head and at least three tails =