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Finding the Fourth Proportional to 709.12, 1,063.68 and 420.80

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Solution

The fourth proportional to 709.12, 1,063.68 and 420.80 is: 631.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    709.12 : 1,063.68 = 420.80 : x
  2. Step 2: Convert to fraction form
    709.12/1,063.68 = 420.80/x
  3. Step 3: Cross multiply
    709.12x = 1,063.68 × 420.80
  4. Step 4: Simplify right side
    709.12x = 447,596.54
  5. Step 5: Solve for x
    x = 447,596.54/709.12
  6. Step 6: Final answer
    x = 631.20

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.