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Finding the Fourth Proportional to 83.58, 115.20 and 78.90

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Solution

The fourth proportional to 83.58, 115.20 and 78.90 is: 108.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    83.58 : 115.20 = 78.90 : x
  2. Step 2: Convert to fraction form
    83.58/115.20 = 78.90/x
  3. Step 3: Cross multiply
    83.58x = 115.20 × 78.90
  4. Step 4: Simplify right side
    83.58x = 9,089.28
  5. Step 5: Solve for x
    x = 9,089.28/83.58
  6. Step 6: Final answer
    x = 108.75

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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.