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Finding the Fourth Proportional to 81.40, 112.08 and 56.80

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Solution

The fourth proportional to 81.40, 112.08 and 56.80 is: 78.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.40 : 112.08 = 56.80 : x
  2. Step 2: Convert to fraction form
    81.40/112.08 = 56.80/x
  3. Step 3: Cross multiply
    81.40x = 112.08 × 56.80
  4. Step 4: Simplify right side
    81.40x = 6,366.14
  5. Step 5: Solve for x
    x = 6,366.14/81.40
  6. Step 6: Final answer
    x = 78.21

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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.