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Finding the Fourth Proportional to 100.71, 138.81 and 71.21

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Solution

The fourth proportional to 100.71, 138.81 and 71.21 is: 98.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.71 : 138.81 = 71.21 : x
  2. Step 2: Convert to fraction form
    100.71/138.81 = 71.21/x
  3. Step 3: Cross multiply
    100.71x = 138.81 × 71.21
  4. Step 4: Simplify right side
    100.71x = 9,884.66
  5. Step 5: Solve for x
    x = 9,884.66/100.71
  6. Step 6: Final answer
    x = 98.15

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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.