A basket contain 4 red, 5 blue and 3 green marbles. If 2 marbles are drawn at random what is the probability that both are red ?
Answer & explanation
Correct answer: option 3
Total number 4 of marbles = 4 + 5 + 3 = 11
Probability of drawing 2 marbles = ${^12C_{2}}$
= \(\frac{ 12! }{2! ( 10)!}\)
= 66
Number of red marbles = 4
Probability of drawing 2 marbles = ${^4C_{2}}$
= \(\frac{ 4! }{2! ( 2)!}\)
= 6
probability that both are red marbles = \(\frac{ 6 }{66}\)
= \(\frac{ 1 }{11}\)
The correct answer is option (3) : $\frac{1}{11}$