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Finding the Fourth Proportional to 115.71, 159.71 and 78.90

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Solution

The fourth proportional to 115.71, 159.71 and 78.90 is: 108.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    115.71 : 159.71 = 78.90 : x
  2. Step 2: Convert to fraction form
    115.71/159.71 = 78.90/x
  3. Step 3: Cross multiply
    115.71x = 159.71 × 78.90
  4. Step 4: Simplify right side
    115.71x = 12,600.72
  5. Step 5: Solve for x
    x = 12,600.72/115.71
  6. Step 6: Final answer
    x = 108.90

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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.