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Finding the Fourth Proportional to 680.10, 1,020.15 and 420.90

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Solution

The fourth proportional to 680.10, 1,020.15 and 420.90 is: 631.35

Step by Step Solution

  1. Step 1: Write the proportion equation
    680.10 : 1,020.15 = 420.90 : x
  2. Step 2: Convert to fraction form
    680.10/1,020.15 = 420.90/x
  3. Step 3: Cross multiply
    680.10x = 1,020.15 × 420.90
  4. Step 4: Simplify right side
    680.10x = 429,381.14
  5. Step 5: Solve for x
    x = 429,381.14/680.10
  6. Step 6: Final answer
    x = 631.35

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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.