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Finding the Fourth Proportional to 100.40, 138.68 and 71.42

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Solution

The fourth proportional to 100.40, 138.68 and 71.42 is: 98.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.40 : 138.68 = 71.42 : x
  2. Step 2: Convert to fraction form
    100.40/138.68 = 71.42/x
  3. Step 3: Cross multiply
    100.40x = 138.68 × 71.42
  4. Step 4: Simplify right side
    100.40x = 9,903.48
  5. Step 5: Solve for x
    x = 9,903.48/100.40
  6. Step 6: Final answer
    x = 98.65

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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.