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Finding the Fourth Proportional to 820.80, 1,132.80 and 643.20

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Solution

The fourth proportional to 820.80, 1,132.80 and 643.20 is: 887.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    820.80 : 1,132.80 = 643.20 : x
  2. Step 2: Convert to fraction form
    820.80/1,132.80 = 643.20/x
  3. Step 3: Cross multiply
    820.80x = 1,132.80 × 643.20
  4. Step 4: Simplify right side
    820.80x = 728,616.96
  5. Step 5: Solve for x
    x = 728,616.96/820.80
  6. Step 6: Final answer
    x = 887.69

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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.