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Finding the Fourth Proportional to 1,311, 1,966.50 and 399

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Solution

The fourth proportional to 1,311, 1,966.50 and 399 is: 598.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,311 : 1,966.50 = 399 : x
  2. Step 2: Convert to fraction form
    1,311/1,966.50 = 399/x
  3. Step 3: Cross multiply
    1,311x = 1,966.50 × 399
  4. Step 4: Simplify right side
    1,311x = 784,633.50
  5. Step 5: Solve for x
    x = 784,633.50/1,311
  6. Step 6: Final answer
    x = 598.50

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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.