1
$\begingroup$

Is a simple way to solve the problem. I tried to solve the problem, but got an incorrect answer.

Randomly choosing two numbers from the set {1, 3, 5, 7, 9} with replacement, what is the probability that the product is greater than 40? Express your answer as a percent.

  • 4
    Please post your answer with full working so that people can explain why it is wrong. – 2017-02-28

1 Answers 1

1

Let A and B, be the two numbers that randomly selected with replacement. $\Pr(A \times B > 40) = \dfrac{|\{(9,9),(9,7),(9,5),(7,9),(7,7),(5,9)\}|}{\text{Total}} = \dfrac{6}{5*5} =\dfrac{6}{25} = 24\%$