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Finding the Fourth Proportional to 87.71, 121.21 and 72.15

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Solution

The fourth proportional to 87.71, 121.21 and 72.15 is: 99.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.71 : 121.21 = 72.15 : x
  2. Step 2: Convert to fraction form
    87.71/121.21 = 72.15/x
  3. Step 3: Cross multiply
    87.71x = 121.21 × 72.15
  4. Step 4: Simplify right side
    87.71x = 8,744.70
  5. Step 5: Solve for x
    x = 8,744.70/87.71
  6. Step 6: Final answer
    x = 99.70

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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.