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Finding the Fourth Proportional to 87.15, 120.18 and 78.45

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Solution

The fourth proportional to 87.15, 120.18 and 78.45 is: 108.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.15 : 120.18 = 78.45 : x
  2. Step 2: Convert to fraction form
    87.15/120.18 = 78.45/x
  3. Step 3: Cross multiply
    87.15x = 120.18 × 78.45
  4. Step 4: Simplify right side
    87.15x = 9,428.12
  5. Step 5: Solve for x
    x = 9,428.12/87.15
  6. Step 6: Final answer
    x = 108.18

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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.