A bag contains 6 red marbles and 4 white marbles.

BTGModeratorVI wrote: ↑

Wed May 13, 2020 11:03 am

A bag contains 6 red marbles and 4 white marbles. Alpha selects a marble from the bag at random, records its color and places it back in the bag. Then, Navarro selects a marble from the bag at random. What is the probability that Alpha and Navarro both select white marbles.

A. 4/25
B. 9/25
C. 2/5
D. 3/5
E. 4/5

Answer: A
Source: Princeton Review

For Alpha, the probability of drawing a white marble = 4/(4 + 6) = 4/10 = 2/5;

Since the drawn marble is replaced, we again have 6 red marbles and 4 white marbles in the bag.

Similarly, for Navarro, the probability of drawing a white marble = 4/(4 + 6) = 4/10 = 2/5;

Thus, the probability that Alpha and Navarro both select white marbles = 2/5*2/5 = 4/25

The correct answer: A

Hope this helps!

-Jay
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BTGModeratorVI wrote: ↑

Wed May 13, 2020 11:03 am

A bag contains 6 red marbles and 4 white marbles. Alpha selects a marble from the bag at random, records its color and places it back in the bag. Then, Navarro selects a marble from the bag at random. What is the probability that Alpha and Navarro both select white marbles.

A. 4/25
B. 9/25
C. 2/5
D. 3/5
E. 4/5

Answer: A
Source: Princeton Review

P(both are white) = P(1st marble is white AND 2nd marble is white
= P(1st marble is white) x P(2nd marble is white)
= 4/10 x 4/10
= 16/100
= 4/25


Answer: A

Cheers,
Brent

BTGModeratorVI wrote: ↑

Wed May 13, 2020 11:03 am

A bag contains 6 red marbles and 4 white marbles. Alpha selects a marble from the bag at random, records its color and places it back in the bag. Then, Navarro selects a marble from the bag at random. What is the probability that Alpha and Navarro both select white marbles.

A. 4/25
B. 9/25
C. 2/5
D. 3/5
E. 4/5

Answer: A

Solution:

The probability that both select white marbles is 4/10 x 4/10 = 2/5 x 2/5 = 4/25.

Answer: A