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Finding the Fourth Proportional to 688.70, 1,031.70 and 640.10

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Solution

The fourth proportional to 688.70, 1,031.70 and 640.10 is: 958.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    688.70 : 1,031.70 = 640.10 : x
  2. Step 2: Convert to fraction form
    688.70/1,031.70 = 640.10/x
  3. Step 3: Cross multiply
    688.70x = 1,031.70 × 640.10
  4. Step 4: Simplify right side
    688.70x = 660,391.17
  5. Step 5: Solve for x
    x = 660,391.17/688.70
  6. Step 6: Final answer
    x = 958.90

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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.