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There are 30 students in a class. Two monitors  are selected. One is girl and one is boy. Number of boys are 20 and number of girls are 10. In how many ways can monitors be selected?

There are 30 students in a class. Two monitors  are selected. One is girl and one is boy. Number of boys are 20 and number of girls are 10. In how many ways can monitors be selected? Correct Answer 200

Total number of students: 30

Number of monitors  are selected : 2

Number of boys = 20; number of girls = 10

To find:

Number of ways to select monitors 

Formula used:

nCr = n !/ r ! (n – r) !

Calculation:

Select one monitor from boy and one monitor from girl

∴ 20C1 × 10C1 =

                         =

                         = 20 × 10

                            = 200

∴ Total number of ways to select monitors  are 200

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