Consider 21 different pearls on a necklace. How many ways can the pearls be placed in on this necklace such that 3 specific pearls always remain together?

Explanation

To solve the problem of arranging 21 different pearls on a necklace such that 3 specific pearls always remain together, we can follow these steps:

### Step-by-Step Solution:

1. **Treat the 3 Specific Pearls as One Unit**: Since the 3 specific pearls must always remain together, we can consider them as a single unit. This reduces the problem to arranging this unit along with the other pearls.

2. **Count the Total Units**: Initially, we have 21 pearls. By grouping the 3 specific pearls together, we now have:
- 1 unit (the group of 3 pearls) + 18 other pearls = 19 units in total.
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