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Finding the Fourth Proportional to 680.40, 1,020.42 and 315.12

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Solution

The fourth proportional to 680.40, 1,020.42 and 315.12 is: 472.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    680.40 : 1,020.42 = 315.12 : x
  2. Step 2: Convert to fraction form
    680.40/1,020.42 = 315.12/x
  3. Step 3: Cross multiply
    680.40x = 1,020.42 × 315.12
  4. Step 4: Simplify right side
    680.40x = 321,554.75
  5. Step 5: Solve for x
    x = 321,554.75/680.40
  6. Step 6: Final answer
    x = 472.60

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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.