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Finding the Fourth Proportional to 1,211.91, 1,817.48 and 390

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Solution

The fourth proportional to 1,211.91, 1,817.48 and 390 is: 584.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,211.91 : 1,817.48 = 390 : x
  2. Step 2: Convert to fraction form
    1,211.91/1,817.48 = 390/x
  3. Step 3: Cross multiply
    1,211.91x = 1,817.48 × 390
  4. Step 4: Simplify right side
    1,211.91x = 708,818.18
  5. Step 5: Solve for x
    x = 708,818.18/1,211.91
  6. Step 6: Final answer
    x = 584.88

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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.