Mean of: 12, 15, 18, 20, 25.

## The reasoning The **mean** (or average) is the sum of all values divided by how many values you have. **Step 1:** Add all the numbers: 12 + 15 + 18 + 20 + 25 = 90 **Step 2:** Count how many numbers there are: We have 5 numbers. **Step 3:** Divide the sum by the count: Mean = 90 ÷ 5 = **18** This is the **arithmetic mean** principle — redistribute the total equally among all items. ## Why the wrong options tempt you **A) 17** — You might get this if you miscounted and divided by 6 instead of 5, or made an addition error. **C) 19** — This could happen if you added incorrectly (maybe getting 95 instead of 90). **D) 20** — This is just the middle value when arranged in order (the median), not the mean! Don't confuse these two different measures. ## Quick takeaway **Mean = Sum of all values ÷ Number of values** — always add everything first, then divide by how many numbers you counted.