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Finding the Fourth Proportional to 1,421.56, 1,961.11 and 861.67

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Solution

The fourth proportional to 1,421.56, 1,961.11 and 861.67 is: 1,188.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,421.56 : 1,961.11 = 861.67 : x
  2. Step 2: Convert to fraction form
    1,421.56/1,961.11 = 861.67/x
  3. Step 3: Cross multiply
    1,421.56x = 1,961.11 × 861.67
  4. Step 4: Simplify right side
    1,421.56x = 1,689,829.65
  5. Step 5: Solve for x
    x = 1,689,829.65/1,421.56
  6. Step 6: Final answer
    x = 1,188.71

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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.