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Finding the Fourth Proportional to 1,211.78, 1,671.90 and 687.80

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Solution

The fourth proportional to 1,211.78, 1,671.90 and 687.80 is: 948.96

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,211.78 : 1,671.90 = 687.80 : x
  2. Step 2: Convert to fraction form
    1,211.78/1,671.90 = 687.80/x
  3. Step 3: Cross multiply
    1,211.78x = 1,671.90 × 687.80
  4. Step 4: Simplify right side
    1,211.78x = 1,149,932.82
  5. Step 5: Solve for x
    x = 1,149,932.82/1,211.78
  6. Step 6: Final answer
    x = 948.96

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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.