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Finding the Fourth Proportional to 100.56, 138.78 and 61.74

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Solution

The fourth proportional to 100.56, 138.78 and 61.74 is: 85.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.56 : 138.78 = 61.74 : x
  2. Step 2: Convert to fraction form
    100.56/138.78 = 61.74/x
  3. Step 3: Cross multiply
    100.56x = 138.78 × 61.74
  4. Step 4: Simplify right side
    100.56x = 8,568.28
  5. Step 5: Solve for x
    x = 8,568.28/100.56
  6. Step 6: Final answer
    x = 85.21

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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.