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Finding the Fourth Proportional to 1,392.94, 1,921.87 and 861.56

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Solution

The fourth proportional to 1,392.94, 1,921.87 and 861.56 is: 1,188.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,392.94 : 1,921.87 = 861.56 : x
  2. Step 2: Convert to fraction form
    1,392.94/1,921.87 = 861.56/x
  3. Step 3: Cross multiply
    1,392.94x = 1,921.87 × 861.56
  4. Step 4: Simplify right side
    1,392.94x = 1,655,810.68
  5. Step 5: Solve for x
    x = 1,655,810.68/1,392.94
  6. Step 6: Final answer
    x = 1,188.72

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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.