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Finding the Fourth Proportional to 1,187.40, 1,781.87 and 639.97

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Solution

The fourth proportional to 1,187.40, 1,781.87 and 639.97 is: 960.36

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,187.40 : 1,781.87 = 639.97 : x
  2. Step 2: Convert to fraction form
    1,187.40/1,781.87 = 639.97/x
  3. Step 3: Cross multiply
    1,187.40x = 1,781.87 × 639.97
  4. Step 4: Simplify right side
    1,187.40x = 1,140,339.29
  5. Step 5: Solve for x
    x = 1,140,339.29/1,187.40
  6. Step 6: Final answer
    x = 960.36

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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.