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Arun says the number of ways to choose 2 class monitors (with the same duties) from 30 students is $30 \times 29 = 870$ . What is the correct number?

Competition practicePermutations & Combinations

A60
B900
C435
D870

Step-by-Step Solution

The two monitors have the same role, so order does not matter:

^{30} C_{2} = \frac{870}{2} = 435

.

Answer: C) 435

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