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Finding the Fourth Proportional to 909.20, 1,363.80 and 781.20

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Solution

The fourth proportional to 909.20, 1,363.80 and 781.20 is: 1,171.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    909.20 : 1,363.80 = 781.20 : x
  2. Step 2: Convert to fraction form
    909.20/1,363.80 = 781.20/x
  3. Step 3: Cross multiply
    909.20x = 1,363.80 × 781.20
  4. Step 4: Simplify right side
    909.20x = 1,065,400.56
  5. Step 5: Solve for x
    x = 1,065,400.56/909.20
  6. Step 6: Final answer
    x = 1,171.80

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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.