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Finding the Fourth Proportional to 1,687.28, 2,531.16 and 821

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Solution

The fourth proportional to 1,687.28, 2,531.16 and 821 is: 1,231.62

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,687.28 : 2,531.16 = 821 : x
  2. Step 2: Convert to fraction form
    1,687.28/2,531.16 = 821/x
  3. Step 3: Cross multiply
    1,687.28x = 2,531.16 × 821
  4. Step 4: Simplify right side
    1,687.28x = 2,078,082.36
  5. Step 5: Solve for x
    x = 2,078,082.36/1,687.28
  6. Step 6: Final answer
    x = 1,231.62

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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.