There are 5 duplicate and 10 of original items in an automobile shop and 3 items are bought at random by a customer. The probability that none of the items is duplicate is: |
20/91 22/91 24/91 89/91 |
24/91 |
P (none is duplicate) = $\frac{{^{10}C}_3}{{^{15}C}_3}=\frac{10×9×8}{15×14×13}=\frac{24}{91}$ |