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Finding the Fourth Proportional to 872.80, 1,311.90 and 856.60

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Solution

The fourth proportional to 872.80, 1,311.90 and 856.60 is: 1,287.55

Step by Step Solution

  1. Step 1: Write the proportion equation
    872.80 : 1,311.90 = 856.60 : x
  2. Step 2: Convert to fraction form
    872.80/1,311.90 = 856.60/x
  3. Step 3: Cross multiply
    872.80x = 1,311.90 × 856.60
  4. Step 4: Simplify right side
    872.80x = 1,123,773.54
  5. Step 5: Solve for x
    x = 1,123,773.54/872.80
  6. Step 6: Final answer
    x = 1,287.55

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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.