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Finding the Fourth Proportional to 781.35, 1,172.25 and 390.89

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Solution

The fourth proportional to 781.35, 1,172.25 and 390.89 is: 586.44

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.35 : 1,172.25 = 390.89 : x
  2. Step 2: Convert to fraction form
    781.35/1,172.25 = 390.89/x
  3. Step 3: Cross multiply
    781.35x = 1,172.25 × 390.89
  4. Step 4: Simplify right side
    781.35x = 458,214.94
  5. Step 5: Solve for x
    x = 458,214.94/781.35
  6. Step 6: Final answer
    x = 586.44

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Half scale
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Double scale
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1.5x scale

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.