A teacher takes three children from her class to a zoo at a time, but she does not take the same three children to the zoo more than once. She finds that she went to the zoo 84 times more than a particular child has gone to the zoo. The number of children n her class is a. `12` b. `10` c. `60` d. none of these

Explanation

To solve the problem step by step, we can follow these calculations:

### Step 1: Understand the Problem
The teacher takes 3 children at a time from a class of `n` children. The number of unique groups of 3 children that can be formed from `n` children is given by the combination formula \( C(n, 3) \).

### Step 2: Write the Combination Formula
The number of ways to choose 3 children from `n` is:
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