Sagot :
Answer:
Assuming random selection, no prior knowledge, order does not matter.
a) 22*21*20*19 or 22 C 4 - which is 7315 (note: total combinations , good or bad would be 25 C 4 or 12650 )
b) 2 bad units ( 3*2 or 3 C 2 - 3) times 2 good units ( 22*21 or 22C2 - 231) or 693
c) Same as asking how many ways to get 2 or less bad units. That would be 0 bad units (answer to a) plus 2 bad units (answer b) , plus 1 bad unit ( 3C1 * 22C3 or 1543), which together equal 9551
Step-by-step explanation: