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Finding the Fourth Proportional to 872, 1,308 and 861.20

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Solution

The fourth proportional to 872, 1,308 and 861.20 is: 1,291.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    872 : 1,308 = 861.20 : x
  2. Step 2: Convert to fraction form
    872/1,308 = 861.20/x
  3. Step 3: Cross multiply
    872x = 1,308 × 861.20
  4. Step 4: Simplify right side
    872x = 1,126,449.60
  5. Step 5: Solve for x
    x = 1,126,449.60/872
  6. Step 6: Final answer
    x = 1,291.80

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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.