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Finding the Fourth Proportional to 213.75, 320.64 and 76.80

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Solution

The fourth proportional to 213.75, 320.64 and 76.80 is: 115.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    213.75 : 320.64 = 76.80 : x
  2. Step 2: Convert to fraction form
    213.75/320.64 = 76.80/x
  3. Step 3: Cross multiply
    213.75x = 320.64 × 76.80
  4. Step 4: Simplify right side
    213.75x = 24,625.15
  5. Step 5: Solve for x
    x = 24,625.15/213.75
  6. Step 6: Final answer
    x = 115.21

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.