Biggest common factor of (18, 20 and 28)/2 is equal to

Options

A. 4
B. 3
C. 1
D. 2

Answer

To find the biggest common factor (also known as the highest common factor, HCF) of the numbers 18, 20, and 28, and then divide that result by 2, we can follow these steps:

### Step-by-Step Solution:

1. **Find the Prime Factorization of Each Number:**
- For **18**:
- 18 = 2 × 3 × 3 = 2 × 3²
- For **20**:
- 20 = 2 × 2 × 5 = 2² × 5
- For **28**:
- 28 = 2 × 2 × 7 = 2² × 7

2. **Identify the Common Factors:**
- The common prime factor for all three numbers is **2**.
- The other prime factors (3, 5, and 7) are not common to all three numbers.

3. **Determine the Biggest Common Factor:**
- The biggest common factor (HCF) of 18, 20, and 28 is **2**.

4. **Divide the HCF by 2:**
- Now, we divide the HCF by 2:
- HCF = 2
- HCF / 2 = 2 / 2 = 1

5. **Final Answer:**
- The biggest common factor of (18, 20, and 28) divided by 2 is **1**.