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Finding the Fourth Proportional to 687.80, 1,031.70 and 680.60

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Solution

The fourth proportional to 687.80, 1,031.70 and 680.60 is: 1,020.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    687.80 : 1,031.70 = 680.60 : x
  2. Step 2: Convert to fraction form
    687.80/1,031.70 = 680.60/x
  3. Step 3: Cross multiply
    687.80x = 1,031.70 × 680.60
  4. Step 4: Simplify right side
    687.80x = 702,175.02
  5. Step 5: Solve for x
    x = 702,175.02/687.80
  6. Step 6: Final answer
    x = 1,020.90

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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.