There are 10 defective light bulbs in a bin containing 20 light bulbs. In how many ways can you select at most 2 defective light bulbs when you choose 10 light bulbs at random?
Let "X=" the number of defective light bulbs in the sample.
"X=1: \\dbinom{10}{1}\\dbinom{10}{10-1}=10(10)=100"
"X=2: \\dbinom{10}{2}\\dbinom{10}{10-2}=45(45)=2025"
"1+100+2025=2126"
We can select at most 2 defective light bulbs in 2126 ways.
Comments
Leave a comment