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Finding the Fourth Proportional to 809.20, 1,213.80 and 647.20

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Solution

The fourth proportional to 809.20, 1,213.80 and 647.20 is: 970.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    809.20 : 1,213.80 = 647.20 : x
  2. Step 2: Convert to fraction form
    809.20/1,213.80 = 647.20/x
  3. Step 3: Cross multiply
    809.20x = 1,213.80 × 647.20
  4. Step 4: Simplify right side
    809.20x = 785,571.36
  5. Step 5: Solve for x
    x = 785,571.36/809.20
  6. Step 6: Final answer
    x = 970.80

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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.