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Finding the Fourth Proportional to 821.76, 1,231.80 and 389.28

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Solution

The fourth proportional to 821.76, 1,231.80 and 389.28 is: 583.52

Step by Step Solution

  1. Step 1: Write the proportion equation
    821.76 : 1,231.80 = 389.28 : x
  2. Step 2: Convert to fraction form
    821.76/1,231.80 = 389.28/x
  3. Step 3: Cross multiply
    821.76x = 1,231.80 × 389.28
  4. Step 4: Simplify right side
    821.76x = 479,515.10
  5. Step 5: Solve for x
    x = 479,515.10/821.76
  6. Step 6: Final answer
    x = 583.52

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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.