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Finding the Fourth Proportional to 1,108.69, 1,530 and 643.21

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Solution

The fourth proportional to 1,108.69, 1,530 and 643.21 is: 887.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,108.69 : 1,530 = 643.21 : x
  2. Step 2: Convert to fraction form
    1,108.69/1,530 = 643.21/x
  3. Step 3: Cross multiply
    1,108.69x = 1,530 × 643.21
  4. Step 4: Simplify right side
    1,108.69x = 984,107.48
  5. Step 5: Solve for x
    x = 984,107.48/1,108.69
  6. Step 6: Final answer
    x = 887.63

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.