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Finding the Fourth Proportional to 820.71, 1,231.20 and 387.63

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Solution

The fourth proportional to 820.71, 1,231.20 and 387.63 is: 581.51

Step by Step Solution

  1. Step 1: Write the proportion equation
    820.71 : 1,231.20 = 387.63 : x
  2. Step 2: Convert to fraction form
    820.71/1,231.20 = 387.63/x
  3. Step 3: Cross multiply
    820.71x = 1,231.20 × 387.63
  4. Step 4: Simplify right side
    820.71x = 477,250.06
  5. Step 5: Solve for x
    x = 477,250.06/820.71
  6. Step 6: Final answer
    x = 581.51

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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.