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Finding the Fourth Proportional to 1,121.70, 1,682.70 and 391.18

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Solution

The fourth proportional to 1,121.70, 1,682.70 and 391.18 is: 586.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,121.70 : 1,682.70 = 391.18 : x
  2. Step 2: Convert to fraction form
    1,121.70/1,682.70 = 391.18/x
  3. Step 3: Cross multiply
    1,121.70x = 1,682.70 × 391.18
  4. Step 4: Simplify right side
    1,121.70x = 658,228.22
  5. Step 5: Solve for x
    x = 658,228.22/1,121.70
  6. Step 6: Final answer
    x = 586.82

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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.