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Finding the Fourth Proportional to 82.12, 113.28 and 72.40

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Solution

The fourth proportional to 82.12, 113.28 and 72.40 is: 99.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    82.12 : 113.28 = 72.40 : x
  2. Step 2: Convert to fraction form
    82.12/113.28 = 72.40/x
  3. Step 3: Cross multiply
    82.12x = 113.28 × 72.40
  4. Step 4: Simplify right side
    82.12x = 8,201.47
  5. Step 5: Solve for x
    x = 8,201.47/82.12
  6. Step 6: Final answer
    x = 99.87

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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.