Question 778589
Total no. of ways in which 2 balls can be selected out of 10 is 10C2 = 45.


Total number of ways in which 2 red or 2 green balls can be selected is 4C2 + 6C2 = 6 + 15 = 21


So the probability of picking up 2 balls of the same color = 21/45 = 7/15