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Finding the Fourth Proportional to 123, 169.78 and 71.28

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Solution

The fourth proportional to 123, 169.78 and 71.28 is: 98.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    123 : 169.78 = 71.28 : x
  2. Step 2: Convert to fraction form
    123/169.78 = 71.28/x
  3. Step 3: Cross multiply
    123x = 169.78 × 71.28
  4. Step 4: Simplify right side
    123x = 12,101.92
  5. Step 5: Solve for x
    x = 12,101.92/123
  6. Step 6: Final answer
    x = 98.39

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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.