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Finding the Fourth Proportional to 978, 1,349.22 and 641.79

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Solution

The fourth proportional to 978, 1,349.22 and 641.79 is: 885.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    978 : 1,349.22 = 641.79 : x
  2. Step 2: Convert to fraction form
    978/1,349.22 = 641.79/x
  3. Step 3: Cross multiply
    978x = 1,349.22 × 641.79
  4. Step 4: Simplify right side
    978x = 865,915.90
  5. Step 5: Solve for x
    x = 865,915.90/978
  6. Step 6: Final answer
    x = 885.39

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.