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Finding the Fourth Proportional to 712.80, 1,069.20 and 664.80

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Solution

The fourth proportional to 712.80, 1,069.20 and 664.80 is: 997.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    712.80 : 1,069.20 = 664.80 : x
  2. Step 2: Convert to fraction form
    712.80/1,069.20 = 664.80/x
  3. Step 3: Cross multiply
    712.80x = 1,069.20 × 664.80
  4. Step 4: Simplify right side
    712.80x = 710,804.16
  5. Step 5: Solve for x
    x = 710,804.16/712.80
  6. Step 6: Final answer
    x = 997.20

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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.