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Finding the Fourth Proportional to 81.40, 112.40 and 76.80

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Solution

The fourth proportional to 81.40, 112.40 and 76.80 is: 106.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.40 : 112.40 = 76.80 : x
  2. Step 2: Convert to fraction form
    81.40/112.40 = 76.80/x
  3. Step 3: Cross multiply
    81.40x = 112.40 × 76.80
  4. Step 4: Simplify right side
    81.40x = 8,632.32
  5. Step 5: Solve for x
    x = 8,632.32/81.40
  6. Step 6: Final answer
    x = 106.05

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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.