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Finding the Fourth Proportional to 1,280.78, 1,767.51 and 721.36

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Solution

The fourth proportional to 1,280.78, 1,767.51 and 721.36 is: 995.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,280.78 : 1,767.51 = 721.36 : x
  2. Step 2: Convert to fraction form
    1,280.78/1,767.51 = 721.36/x
  3. Step 3: Cross multiply
    1,280.78x = 1,767.51 × 721.36
  4. Step 4: Simplify right side
    1,280.78x = 1,275,002.18
  5. Step 5: Solve for x
    x = 1,275,002.18/1,280.78
  6. Step 6: Final answer
    x = 995.49

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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.