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Finding the Fourth Proportional to 838.69, 1,257.21 and 428.02

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Solution

The fourth proportional to 838.69, 1,257.21 and 428.02 is: 641.61

Step by Step Solution

  1. Step 1: Write the proportion equation
    838.69 : 1,257.21 = 428.02 : x
  2. Step 2: Convert to fraction form
    838.69/1,257.21 = 428.02/x
  3. Step 3: Cross multiply
    838.69x = 1,257.21 × 428.02
  4. Step 4: Simplify right side
    838.69x = 538,111.02
  5. Step 5: Solve for x
    x = 538,111.02/838.69
  6. Step 6: Final answer
    x = 641.61

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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.