Question

There are 11pens in a box.
8 are to black and 3 are red.
Two pens are taken out. work out
the probability that two are the same color.​

Answer 1

Answer:

If both pens are the same color, it means that they are either black and black or red and red.If without replacement,pr. of first black and second black is

8/11 and 7/10.Also, the pr of the first red and sencond red pen= 3/11 and 2/10.

Therefore pr. of bb or rr

(8/11×7/10)+(3/11×2/10)

56/110+6/110 =31/50