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Finding the Fourth Proportional to 1,121.49, 1,680.84 and 390.21

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Solution

The fourth proportional to 1,121.49, 1,680.84 and 390.21 is: 584.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,121.49 : 1,680.84 = 390.21 : x
  2. Step 2: Convert to fraction form
    1,121.49/1,680.84 = 390.21/x
  3. Step 3: Cross multiply
    1,121.49x = 1,680.84 × 390.21
  4. Step 4: Simplify right side
    1,121.49x = 655,880.58
  5. Step 5: Solve for x
    x = 655,880.58/1,121.49
  6. Step 6: Final answer
    x = 584.83

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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.