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Finding the Fourth Proportional to 1,187.80, 1,781.70 and 639.22

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Solution

The fourth proportional to 1,187.80, 1,781.70 and 639.22 is: 958.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,187.80 : 1,781.70 = 639.22 : x
  2. Step 2: Convert to fraction form
    1,187.80/1,781.70 = 639.22/x
  3. Step 3: Cross multiply
    1,187.80x = 1,781.70 × 639.22
  4. Step 4: Simplify right side
    1,187.80x = 1,138,898.27
  5. Step 5: Solve for x
    x = 1,138,898.27/1,187.80
  6. Step 6: Final answer
    x = 958.83

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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.