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Finding the Fourth Proportional to 1,187.78, 1,781.78 and 407.75

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Solution

The fourth proportional to 1,187.78, 1,781.78 and 407.75 is: 611.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,187.78 : 1,781.78 = 407.75 : x
  2. Step 2: Convert to fraction form
    1,187.78/1,781.78 = 407.75/x
  3. Step 3: Cross multiply
    1,187.78x = 1,781.78 × 407.75
  4. Step 4: Simplify right side
    1,187.78x = 726,520.80
  5. Step 5: Solve for x
    x = 726,520.80/1,187.78
  6. Step 6: Final answer
    x = 611.66

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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.