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Finding the Fourth Proportional to 76.20, 105.20 and 56.80

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Solution

The fourth proportional to 76.20, 105.20 and 56.80 is: 78.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    76.20 : 105.20 = 56.80 : x
  2. Step 2: Convert to fraction form
    76.20/105.20 = 56.80/x
  3. Step 3: Cross multiply
    76.20x = 105.20 × 56.80
  4. Step 4: Simplify right side
    76.20x = 5,975.36
  5. Step 5: Solve for x
    x = 5,975.36/76.20
  6. Step 6: Final answer
    x = 78.42

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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.