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Finding the Fourth Proportional to 812.80, 1,217.40 and 427.60

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Solution

The fourth proportional to 812.80, 1,217.40 and 427.60 is: 640.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    812.80 : 1,217.40 = 427.60 : x
  2. Step 2: Convert to fraction form
    812.80/1,217.40 = 427.60/x
  3. Step 3: Cross multiply
    812.80x = 1,217.40 × 427.60
  4. Step 4: Simplify right side
    812.80x = 520,560.24
  5. Step 5: Solve for x
    x = 520,560.24/812.80
  6. Step 6: Final answer
    x = 640.45

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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.