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Finding the Fourth Proportional to 1,420.79, 1,961.06 and 861.28

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Solution

The fourth proportional to 1,420.79, 1,961.06 and 861.28 is: 1,188.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,420.79 : 1,961.06 = 861.28 : x
  2. Step 2: Convert to fraction form
    1,420.79/1,961.06 = 861.28/x
  3. Step 3: Cross multiply
    1,420.79x = 1,961.06 × 861.28
  4. Step 4: Simplify right side
    1,420.79x = 1,689,012.55
  5. Step 5: Solve for x
    x = 1,689,012.55/1,420.79
  6. Step 6: Final answer
    x = 1,188.79

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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.