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Finding the Fourth Proportional to 123.78, 170.86 and 99.17

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Solution

The fourth proportional to 123.78, 170.86 and 99.17 is: 136.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    123.78 : 170.86 = 99.17 : x
  2. Step 2: Convert to fraction form
    123.78/170.86 = 99.17/x
  3. Step 3: Cross multiply
    123.78x = 170.86 × 99.17
  4. Step 4: Simplify right side
    123.78x = 16,944.87
  5. Step 5: Solve for x
    x = 16,944.87/123.78
  6. Step 6: Final answer
    x = 136.90

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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.