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Finding the Fourth Proportional to 78.49, 117.56 and 39.90

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Solution

The fourth proportional to 78.49, 117.56 and 39.90 is: 59.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.49 : 117.56 = 39.90 : x
  2. Step 2: Convert to fraction form
    78.49/117.56 = 39.90/x
  3. Step 3: Cross multiply
    78.49x = 117.56 × 39.90
  4. Step 4: Simplify right side
    78.49x = 4,690.54
  5. Step 5: Solve for x
    x = 4,690.54/78.49
  6. Step 6: Final answer
    x = 59.76

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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.