A gardener is going to plant 2 red rosebushes and 2 white rosebushes. If the gardener is to select each of the bushes at

[VJesus12]

A gardener is going to plant 2 red rosebushes and 2 white rosebushes. If the gardener is to select each of the bushes at random, one at a time, and plant them in a row, what is the probability that the 2 rosebushes in the middle of the row will be the red rosebushes?

A. \(\dfrac1{12}\)

B. \(\dfrac16\)

C. \(\dfrac15\)

D. \(\dfrac13\)

E. \(\dfrac12\)

Answer: B

Source: GMAT Paper Tests

[Brent@GMATPrepNow]

A gardener is going to plant 2 red rosebushes and 2 white rosebushes. If the gardener is to select each of the bushes at random, one at a time, and plant them in a row, what is the probability that the 2 rosebushes in the middle of the row will be the red rosebushes?

A. \(\dfrac1{12}\)

B. \(\dfrac16\)

C. \(\dfrac15\)

D. \(\dfrac13\)

E. \(\dfrac12\)

Answer: B

Source: GMAT Paper Tests

Let's apply some probability rules:

P(2 middle bushes are red) = P(1st bush is white AND 2nd bush is red AND 3rd bush is red AND 4th bush is white)
= P(1st bush is white) x P(2nd bush is red) x P(3rd bush is red) x P(4th bush is white)
= 2/4 x 2/3 x 1/2 x 1/1
= 1/6

Answer: B

Cheers,
Brent