A university warehouse has received a shipment of 25 printer

A university warehouse has received a shipment of 25 printers, of which 10 are laser, 8 are inkjet and 7 are other models.

A. How many ways are there to select 3 lasers out of 10 laser printers?

B. How many ways are there to select 3 lasers, 4 injects and 2 others out of 25 printers?

Solution

a) to select 3 out of 10 we can use combinationations and the answer will be 10C3 = 10!/[7!*3!] = 10*9*8/6= 120

B) 10 LASER 8 INJET 7 OTHER

SO WE HAVE TO CHOSE 3 LASER 4 INJET AND 2 OTHER

COMBINATION WILL BE 10C3*8C4*7C2 = 120*21*70 =176400