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Finding the Fourth Proportional to 100.61, 138.70 and 71.45

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Solution

The fourth proportional to 100.61, 138.70 and 71.45 is: 98.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.61 : 138.70 = 71.45 : x
  2. Step 2: Convert to fraction form
    100.61/138.70 = 71.45/x
  3. Step 3: Cross multiply
    100.61x = 138.70 × 71.45
  4. Step 4: Simplify right side
    100.61x = 9,910.28
  5. Step 5: Solve for x
    x = 9,910.28/100.61
  6. Step 6: Final answer
    x = 98.50

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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.