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Finding the Fourth Proportional to 810.78, 1,209.60 and 687.66

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Solution

The fourth proportional to 810.78, 1,209.60 and 687.66 is: 1,025.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    810.78 : 1,209.60 = 687.66 : x
  2. Step 2: Convert to fraction form
    810.78/1,209.60 = 687.66/x
  3. Step 3: Cross multiply
    810.78x = 1,209.60 × 687.66
  4. Step 4: Simplify right side
    810.78x = 831,793.54
  5. Step 5: Solve for x
    x = 831,793.54/810.78
  6. Step 6: Final answer
    x = 1,025.92

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.