sachin_yadav wrote:There is a total of 120 marbles in a box, each of which is red, green, blue, or white. If one marble is drawn from the box at random, the probability that it will be white is 1/4 and the probability that it will be green is 1/3. What is the probability that the marble will be either red or blue?
(A) 1/6
(B) 1/4
(C) 2/7
(D) 1/3
(E) 5/12
Since the problem asks for a FRACTION, the total number of marbles can be ANY VALUE.
Let the total number of marbles = the LCM of 3 and 4 = 12.
If one marble is drawn from the box at random, the probability that it will be white is 1/4.
Thus:
W = (1/4)(12) = 3.
If one marble is drawn from the box at random, the probability that it will be green is 1/3.
Thus:
G = (1/3)(12) = 4.
Implication:
Of the 12 marbles, the number that are R or B = 12-3-4 = 5.
Since 5 of the 12 marbles are R or B, we get:
P(R or B) = 5/12.
The correct answer is
E.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at
[email protected].
Student Review #1
Student Review #2
Student Review #3
