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Finding the Fourth Proportional to 672.12, 1,008.36 and 428.40

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Solution

The fourth proportional to 672.12, 1,008.36 and 428.40 is: 642.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    672.12 : 1,008.36 = 428.40 : x
  2. Step 2: Convert to fraction form
    672.12/1,008.36 = 428.40/x
  3. Step 3: Cross multiply
    672.12x = 1,008.36 × 428.40
  4. Step 4: Simplify right side
    672.12x = 431,981.42
  5. Step 5: Solve for x
    x = 431,981.42/672.12
  6. Step 6: Final answer
    x = 642.71

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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.