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Finding the Fourth Proportional to 100.46, 138.69 and 72.78

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Solution

The fourth proportional to 100.46, 138.69 and 72.78 is: 100.48

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.46 : 138.69 = 72.78 : x
  2. Step 2: Convert to fraction form
    100.46/138.69 = 72.78/x
  3. Step 3: Cross multiply
    100.46x = 138.69 × 72.78
  4. Step 4: Simplify right side
    100.46x = 10,093.86
  5. Step 5: Solve for x
    x = 10,093.86/100.46
  6. Step 6: Final answer
    x = 100.48

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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.