Question

8 junior high classes will be chosen to participate in a school improvement survey. There are 21 junior high classes in the school. In how many ways can the classes be chosen?

Answer 1

The classes can be chosen in 203,490 ways

Explanation

The number of combinations of n things chosen r at a time is found using the next formula:

`nCr=(n!)/(r!(n-r)!)`

In this case, we have to choose r = 8 junior high classes from a total of n = 21 classes. Substituting these values into the formula, we get:

`\begin{gathered} _(21)C_8=(21!)/(8!(21-8)!) \\ _(21)C_8=203,490 \end{gathered}`