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Question -

From a class of 12 boys and 10 girls, 10 students are to be chosen for the competition, at least including 4 boys and 4 girls. The 2 girls who won the prizes last year should be included. In how many ways can the selection be made?



Answer -

Given:

Total number of boys =12

Total number of girls= 10

Total number of girlsfor the competition = 10 + 2 = 12

Number of ways = (no.of ways of selecting 6 boys and 2 girls from remaining 12 boys and 8 girls) + (no.of ways of selecting 5 boys and 3 girls from remaining 12 boys and 8 girls) +(no. of ways of selecting 4 boys and 4 girls from remaining 12 boys and 8girls)

Since, two girls arealready selected,

= (12C6 × 8C2)+ (12C5 × 8C3) + (12C4 × 8C4)

By using the formula,

nCr = n!/r!(n – r)!

= (924 × 28) + (792 ×56) + (495 × 70)

= 25872 + 44352 +34650

= 104874

 The total numberof ways of product is 104874 ways.

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