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Finding the Fourth Proportional to 123.18, 169.86 and 78.90

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Solution

The fourth proportional to 123.18, 169.86 and 78.90 is: 108.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    123.18 : 169.86 = 78.90 : x
  2. Step 2: Convert to fraction form
    123.18/169.86 = 78.90/x
  3. Step 3: Cross multiply
    123.18x = 169.86 × 78.90
  4. Step 4: Simplify right side
    123.18x = 13,401.95
  5. Step 5: Solve for x
    x = 13,401.95/123.18
  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.