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Finding the Fourth Proportional to 861.10, 1,188.60 and 640.78

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Solution

The fourth proportional to 861.10, 1,188.60 and 640.78 is: 884.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    861.10 : 1,188.60 = 640.78 : x
  2. Step 2: Convert to fraction form
    861.10/1,188.60 = 640.78/x
  3. Step 3: Cross multiply
    861.10x = 1,188.60 × 640.78
  4. Step 4: Simplify right side
    861.10x = 761,631.11
  5. Step 5: Solve for x
    x = 761,631.11/861.10
  6. Step 6: Final answer
    x = 884.49

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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.