1. Let's understand why we multiply by 3 in certain problems. 2. Multiplying by 3 means you are adding the same number three times. For example, $3 \times 4$ means $4 + 4 + 4$. 3. This is based on the definition of multiplication as repeated addition. 4. If you have a group of items and there are 3 such groups, multiplying by 3 gives the total number of items. 5. For example, if each group has $x$ items, then total items are $3 \times x$. 6. So, multiplying by 3 is a shortcut to adding the same number three times, making calculations faster and easier.