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Finding the Fourth Proportional to 781.78, 1,172.40 and 261.70

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Solution

The fourth proportional to 781.78, 1,172.40 and 261.70 is: 392.46

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.78 : 1,172.40 = 261.70 : x
  2. Step 2: Convert to fraction form
    781.78/1,172.40 = 261.70/x
  3. Step 3: Cross multiply
    781.78x = 1,172.40 × 261.70
  4. Step 4: Simplify right side
    781.78x = 306,817.08
  5. Step 5: Solve for x
    x = 306,817.08/781.78
  6. Step 6: Final answer
    x = 392.46

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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.