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Finding the Fourth Proportional to 821.12, 1,231.44 and 388

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Solution

The fourth proportional to 821.12, 1,231.44 and 388 is: 581.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    821.12 : 1,231.44 = 388 : x
  2. Step 2: Convert to fraction form
    821.12/1,231.44 = 388/x
  3. Step 3: Cross multiply
    821.12x = 1,231.44 × 388
  4. Step 4: Simplify right side
    821.12x = 477,798.72
  5. Step 5: Solve for x
    x = 477,798.72/821.12
  6. Step 6: Final answer
    x = 581.89

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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.