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Finding the Fourth Proportional to 781.10, 1,171.71 and 318.91

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Solution

The fourth proportional to 781.10, 1,171.71 and 318.91 is: 478.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.10 : 1,171.71 = 318.91 : x
  2. Step 2: Convert to fraction form
    781.10/1,171.71 = 318.91/x
  3. Step 3: Cross multiply
    781.10x = 1,171.71 × 318.91
  4. Step 4: Simplify right side
    781.10x = 373,670.04
  5. Step 5: Solve for x
    x = 373,670.04/781.10
  6. Step 6: Final answer
    x = 478.39

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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.