In a box, there are 40 pens in total in four different colors. There are 12 red pens, 9 blue pens, 10 green pens and 9 black pens. If two pens are chosen at random, what is the chance of getting same color pens?
In a box, there are 40 pens in total in four different colors. There are 12 red pens, 9 blue pens, 10 green pens and 9 black pens. If two pens are chosen at random, what is the chance of getting same color pens? Correct Answer 61/260
GIVEN :
Total number of pens = 40
CALCULATION :
Probability of withdrawing 2 pens out of 40 pens = Total outcomes
= 40C2
= (40 × 39)/(2 × 1) = 780
Total possible outcomes = (2 pens from 12 red pens) + (2 pens from 9 blue pens) + (2 pens from 10 green pens) + 2 pens from 9 black pens)
⇒ 12C2 + 9C2 + 10C2 + 9C2
⇒ + + +
⇒ 66 + 36 + 45 + 36 = 183
Required Ratio = (Total possible outcome/Total outcomes)
= 183/780 = 61/260
∴ Required ratio = 61/260