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Finding the Fourth Proportional to 123.20, 169.90 and 78.89

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Solution

The fourth proportional to 123.20, 169.90 and 78.89 is: 108.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    123.20 : 169.90 = 78.89 : x
  2. Step 2: Convert to fraction form
    123.20/169.90 = 78.89/x
  3. Step 3: Cross multiply
    123.20x = 169.90 × 78.89
  4. Step 4: Simplify right side
    123.20x = 13,403.93
  5. Step 5: Solve for x
    x = 13,403.93/123.20
  6. Step 6: Final answer
    x = 108.80

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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.