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Finding the Fourth Proportional to 100.78, 138.98 and 71.30

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Solution

The fourth proportional to 100.78, 138.98 and 71.30 is: 98.33

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.78 : 138.98 = 71.30 : x
  2. Step 2: Convert to fraction form
    100.78/138.98 = 71.30/x
  3. Step 3: Cross multiply
    100.78x = 138.98 × 71.30
  4. Step 4: Simplify right side
    100.78x = 9,909.80
  5. Step 5: Solve for x
    x = 9,909.80/100.78
  6. Step 6: Final answer
    x = 98.33

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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.