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Finding the Fourth Proportional to 680.91, 1,020 and 420.78

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Solution

The fourth proportional to 680.91, 1,020 and 420.78 is: 630.33

Step by Step Solution

  1. Step 1: Write the proportion equation
    680.91 : 1,020 = 420.78 : x
  2. Step 2: Convert to fraction form
    680.91/1,020 = 420.78/x
  3. Step 3: Cross multiply
    680.91x = 1,020 × 420.78
  4. Step 4: Simplify right side
    680.91x = 429,195.60
  5. Step 5: Solve for x
    x = 429,195.60/680.91
  6. Step 6: Final answer
    x = 630.33

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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.