The first three terms of a porportion are 3,5 and 21 respectively. Find its fourth term.

Answer

To find the fourth term of the proportion given the first three terms (3, 5, and 21), we can follow these steps:

### Step-by-Step Solution

1. **Identify the Terms**: We are given three terms of a proportion: 3, 5, and 21. We need to find the fourth term, which we will denote as \( x \).

2. **Set Up the Proportion**: In a proportion, the relationship can be expressed as:
\[ \frac{3}{5} = \frac{21}{x} \]

3. **Cross Multiply**: To solve for \( x \), we will cross-multiply:
\[ 3 \cdot x = 5 \cdot 21 \]

4. **Calculate the Right Side**: Now, we calculate \( 5 \cdot 21 \):
\[ 5 \cdot 21 = 105 \]

5. **Set Up the Equation**: Now we have:
\[ 3x = 105 \]

6. **Solve for \( x \)**: To find \( x \), divide both sides of the equation by 3:
\[ x = \frac{105}{3} \]

7. **Calculate \( x \)**: Now perform the division:
\[ x = 35 \]

8. **Conclusion**: Therefore, the fourth term is \( 35 \).

### Final Answer
The fourth term of the proportion is **35**.

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