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Finding the Fourth Proportional to 78.75, 117.90 and 54.30

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Solution

The fourth proportional to 78.75, 117.90 and 54.30 is: 81.29

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.75 : 117.90 = 54.30 : x
  2. Step 2: Convert to fraction form
    78.75/117.90 = 54.30/x
  3. Step 3: Cross multiply
    78.75x = 117.90 × 54.30
  4. Step 4: Simplify right side
    78.75x = 6,401.97
  5. Step 5: Solve for x
    x = 6,401.97/78.75
  6. Step 6: Final answer
    x = 81.29

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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.