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Finding the Fourth Proportional to 78.54, 117.72 and 42.39

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Solution

The fourth proportional to 78.54, 117.72 and 42.39 is: 63.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.54 : 117.72 = 42.39 : x
  2. Step 2: Convert to fraction form
    78.54/117.72 = 42.39/x
  3. Step 3: Cross multiply
    78.54x = 117.72 × 42.39
  4. Step 4: Simplify right side
    78.54x = 4,989.94
  5. Step 5: Solve for x
    x = 4,989.94/78.54
  6. Step 6: Final answer
    x = 63.54

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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.