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Finding the Fourth Proportional to 1,187.78, 1,639.21 and 663.85

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Solution

The fourth proportional to 1,187.78, 1,639.21 and 663.85 is: 916.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,187.78 : 1,639.21 = 663.85 : x
  2. Step 2: Convert to fraction form
    1,187.78/1,639.21 = 663.85/x
  3. Step 3: Cross multiply
    1,187.78x = 1,639.21 × 663.85
  4. Step 4: Simplify right side
    1,187.78x = 1,088,189.56
  5. Step 5: Solve for x
    x = 1,088,189.56/1,187.78
  6. Step 6: Final answer
    x = 916.15

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.