Question

From a class of 25 students ,10 are to be chosen for an excursion. There are 3 students who decide that either all of them will join or none of them will join. In how many ways can the excursion party be chosen??

Answer 1

Answer:

Step-by-step explanation:

There are two cases.

(a) If the 3 students join the excursion party then the number of combinations will be

P1=C(22,7)

(b) If the 3 students do not join the excursion party.

Then the number of combinations

P2=C(22,10)

If P is the combinations of choosing the excursion party,then

P=P1+P2=C(22,7)+C(22,10)

=22!7!8!+22!10!12!

=22×21×20×19×18×17×16×15!7×6×5×4×3×2×1×15!+22×21×20×19×18×17×16×15×13×12!10×9×8×7×6×5×4×3×2×1×12!

=817190