Posted by **Student** on Sunday, March 4, 2012 at 2:28pm.

Darby guesses the answers to six questions on the math portion of her college entrance exam. Each question is a true or false question. What is the approximate probability that at least 4 of her answers are correct?

A. 0.23

B. 0.34

C. 0.66

D. 0.78

Explanation please??

- Probability -
**MathMate**, Sunday, March 4, 2012 at 4:22pm
The answer is

(n,r)/2^n

Here there are 6 questions, so n=6, and

there are 2^6=64 possible sets of answers.

Since 4 of them are right, the number of combinations with 4 correct out of 6 is

(n,r)=(6,4)=6*5/(1*2)=15

What would be the probability that 4 out of six are correct if the answers are completely random?

## Answer This Question

## Related Questions

- Probability - Darby guesses the answers to six questions on the math portion of...
- Probability - Thank you for the explanation MathMate! Would the answer to this ...
- Math - Darby guesses the answers to six questions on the math portion of her ...
- Math - Darby guesses the answers to six questions on the math portion of her ...
- Statistics - A student is taking a true/false exam with 15 questions. If he ...
- Statistics Algebra 2 - A 10-question multiple choice test has 4 possible ...
- Stat HW for. - 1. A student taking a midterm exam in Ancient History comes to ...
- math - 11. A Certification Exam containing 20 true and false questions. If a ...
- Math - There are six true-false questions on a quiz. Not knowing any of the ...
- Statistical concept 68-95-99.7 - 1. A student taking a midterm exam in Ancient ...

More Related Questions