UPSC NDA Math Model Paper 7

Case -I: We can select one boy and one girl from the given children.
The number of ways of doing so is:
‌3C1×‌2C1=3×2=6
Case -II: We can also select both boys.
The number of ways of doing so is:
‌3C2=3
Therefore, the number of ways of selecting either one girl and one boy or both boys is given by:
6 + 3 = 9
Therefore, the number of ways of selecting two children such that there is at least one boy is 9.