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Finding the Fourth Proportional to 86, 118.72 and 78.16

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Solution

The fourth proportional to 86, 118.72 and 78.16 is: 107.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    86 : 118.72 = 78.16 : x
  2. Step 2: Convert to fraction form
    86/118.72 = 78.16/x
  3. Step 3: Cross multiply
    86x = 118.72 × 78.16
  4. Step 4: Simplify right side
    86x = 9,279.16
  5. Step 5: Solve for x
    x = 9,279.16/86
  6. Step 6: Final answer
    x = 107.90

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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.