# tryin to help my kid with her homework

#### hllywd

##### New Member
1. If you guess the answers at random, what is the probability of getting at least two correct answers on a five question true or false quiz?

2. If you guess the answers at random, what is the probablity of getting at least three correct answers on a five question true or false quiz?

3. A five question multiple choice quiz has five choices for each answer. What is the probablity of correctly guessing at random exactly one correct answer? Exactly two correct answers? Exactly three correct answers?

#### jamesmartinn

##### Member
1)

p(true) = .5
p(false) = .5
n = 5
X = 2

Question is asking P( X > 2)

= P(2) + P(3) + P(4) + P(5)

Use the binomial distribution. These kind of questions are similar to 'coin toss' questions, if that helps.

Follow the same setup for the remaining questions,

best of luck.

#### Akavall

##### New Member
You can use the formula from this link to figure out probablities for P(2) P(3) P(4) P(5).

http://www.knowyourluck.com/coinsnu.html

Btw, you don't really need to do the math to see that the answer to question 2 is 1/2 .