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Finding the Fourth Proportional to 709.50, 979.20 and 399

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Solution

The fourth proportional to 709.50, 979.20 and 399 is: 550.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    709.50 : 979.20 = 399 : x
  2. Step 2: Convert to fraction form
    709.50/979.20 = 399/x
  3. Step 3: Cross multiply
    709.50x = 979.20 × 399
  4. Step 4: Simplify right side
    709.50x = 390,700.80
  5. Step 5: Solve for x
    x = 390,700.80/709.50
  6. Step 6: Final answer
    x = 550.67

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.