Posted by **Angie** on Saturday, June 13, 2009 at 5:53pm.

If four coins are flipped at once, what is the probability that exactly 3 tails will come up?

a. 1/16

b. 1/8

c. 1/4

d. 1/2

The answer is c, but what do you do to get that?

- Math -
**Damon**, Saturday, June 13, 2009 at 6:12pm
Binomial distribution

p(n,k) = C(n,k) p^(k) (1-p)^(n-k)

here n = 4, k = 3, p =.5

C(4,3) = 4!/[3!*1!] = 4 or use Pascal triangle or table of binomial coefs

so

4 (.5)^3*.5

= .25 sure enough c

## Answer this Question

## Related Questions

- Math - 1. When four fan coins are flipped what is the probability of getting ...
- Math: Probablity - A penny, a nickel, and a dime are flipped at the same time. ...
- Math - Four coins fall onto the floor. Find the probability that (a) exactly ...
- math - Six fair coins are flipped, the probability that exactly three coins ...
- Statistics - Suppose Tori has an unfair coin which lands on Tails with ...
- Probability - Suppose that an unfair coin comes up heads 54.1% of the time. The...
- Probability - Two fair coins are flipped simultaneously. This is done repeatedly...
- math - John has 3 unique coins such that the probability of obtaining a head ...
- probability - John has 3 unique coins such that the probability of obtaining a ...
- probability - John has 3 unique coins such that the probability of obtaining a ...

More Related Questions