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Finding the Fourth Proportional to 1,211.90, 1,672.45 and 680.78

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Solution

The fourth proportional to 1,211.90, 1,672.45 and 680.78 is: 939.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,211.90 : 1,672.45 = 680.78 : x
  2. Step 2: Convert to fraction form
    1,211.90/1,672.45 = 680.78/x
  3. Step 3: Cross multiply
    1,211.90x = 1,672.45 × 680.78
  4. Step 4: Simplify right side
    1,211.90x = 1,138,572.99
  5. Step 5: Solve for x
    x = 1,138,572.99/1,211.90
  6. Step 6: Final answer
    x = 939.50

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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.