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Finding the Fourth Proportional to 100.28, 138.23 and 72.21

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Solution

The fourth proportional to 100.28, 138.23 and 72.21 is: 99.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.28 : 138.23 = 72.21 : x
  2. Step 2: Convert to fraction form
    100.28/138.23 = 72.21/x
  3. Step 3: Cross multiply
    100.28x = 138.23 × 72.21
  4. Step 4: Simplify right side
    100.28x = 9,981.59
  5. Step 5: Solve for x
    x = 9,981.59/100.28
  6. Step 6: Final answer
    x = 99.54

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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.