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Question: A drawer contains 5 brown socks and 4 blue socks well mixed. A man reaches the drawer and pulls out ...

A drawer contains 5 brown socks and 4 blue socks well mixed. A man reaches the drawer and pulls out 2 socks at random. What is the probability that they match

A

4/9

B

5/8

C

5/9

D

7/12

Answer

4/9

Explanation

Solution

Out of 9 socks, 2 can be drawn in 9C2{ } ^ { 9 } \mathrm { C } _ { 2 } ways. Two socks drawn from the drawer will match if either both are brown of both are blue. Therefore favourable number of cases is 5C2+4C2{ } ^ { 5 } \mathrm { C } _ { 2 } + { } ^ { 4 } \mathrm { C } _ { 2 } .

Hence the required probability = 5C2+4C29C2=49\frac { { } ^ { 5 } \mathrm { C } _ { 2 } + { } ^ { 4 } \mathrm { C } _ { 2 } } { { } ^ { 9 } \mathrm { C } _ { 2 } } = \frac { 4 } { 9 }