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Finding the Fourth Proportional to 861.36, 1,290.60 and 690

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Solution

The fourth proportional to 861.36, 1,290.60 and 690 is: 1,033.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    861.36 : 1,290.60 = 690 : x
  2. Step 2: Convert to fraction form
    861.36/1,290.60 = 690/x
  3. Step 3: Cross multiply
    861.36x = 1,290.60 × 690
  4. Step 4: Simplify right side
    861.36x = 890,514.00
  5. Step 5: Solve for x
    x = 890,514.00/861.36
  6. Step 6: Final answer
    x = 1,033.85

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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.