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Finding the Fourth Proportional to 78.28, 117.32 and 39.78

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Solution

The fourth proportional to 78.28, 117.32 and 39.78 is: 59.62

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.28 : 117.32 = 39.78 : x
  2. Step 2: Convert to fraction form
    78.28/117.32 = 39.78/x
  3. Step 3: Cross multiply
    78.28x = 117.32 × 39.78
  4. Step 4: Simplify right side
    78.28x = 4,666.99
  5. Step 5: Solve for x
    x = 4,666.99/78.28
  6. Step 6: Final answer
    x = 59.62

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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.