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Finding the Fourth Proportional to 1,187.31, 1,780.96 and 639.75

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Solution

The fourth proportional to 1,187.31, 1,780.96 and 639.75 is: 959.62

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,187.31 : 1,780.96 = 639.75 : x
  2. Step 2: Convert to fraction form
    1,187.31/1,780.96 = 639.75/x
  3. Step 3: Cross multiply
    1,187.31x = 1,780.96 × 639.75
  4. Step 4: Simplify right side
    1,187.31x = 1,139,367.56
  5. Step 5: Solve for x
    x = 1,139,367.56/1,187.31
  6. Step 6: Final answer
    x = 959.62

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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.