The fourth proportional to 0.12, 0.21, 8 is :

Options

A. 8.9
B. 56
C. 14
D. 17

Answer

To find the fourth proportional to the numbers 0.12, 0.21, and 8, we can use the concept of proportions. The fourth proportional can be found using the formula:

If A, B, and C are three numbers, then the fourth proportional D can be found using the relationship:

\[ \frac{A}{B} = \frac{C}{D} \]

### Step-by-Step Solution:

1. **Identify the Values**:
- Let \( A = 0.12 \)
- Let \( B = 0.21 \)
- Let \( C = 8 \)

2. **Set Up the Proportion**:
- We need to find \( D \) such that:
\[ \frac{0.12}{0.21} = \frac{8}{D} \]

3. **Cross Multiply**:
- Cross multiplying gives us:
\[ 0.12 \cdot D = 8 \cdot 0.21 \]

4. **Calculate the Right Side**:
- Calculate \( 8 \cdot 0.21 \):
\[ 8 \cdot 0.21 = 1.68 \]

5. **Rewrite the Equation**:
- Now we have:
\[ 0.12 \cdot D = 1.68 \]

6. **Solve for D**:
- To find \( D \), divide both sides by \( 0.12 \):
\[ D = \frac{1.68}{0.12} \]

7. **Perform the Division**:
- Calculate \( \frac{1.68}{0.12} \):
\[ D = 14 \]

### Final Answer:
The fourth proportional to 0.12, 0.21, and 8 is **14**.