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Finding the Fourth Proportional to 687.69, 1,031.40 and 440.78

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Solution

The fourth proportional to 687.69, 1,031.40 and 440.78 is: 661.08

Step by Step Solution

  1. Step 1: Write the proportion equation
    687.69 : 1,031.40 = 440.78 : x
  2. Step 2: Convert to fraction form
    687.69/1,031.40 = 440.78/x
  3. Step 3: Cross multiply
    687.69x = 1,031.40 × 440.78
  4. Step 4: Simplify right side
    687.69x = 454,620.49
  5. Step 5: Solve for x
    x = 454,620.49/687.69
  6. Step 6: Final answer
    x = 661.08

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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.