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Finding the Fourth Proportional to 1,420.20, 2,129.70 and 690

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Solution

The fourth proportional to 1,420.20, 2,129.70 and 690 is: 1,034.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,420.20 : 2,129.70 = 690 : x
  2. Step 2: Convert to fraction form
    1,420.20/2,129.70 = 690/x
  3. Step 3: Cross multiply
    1,420.20x = 2,129.70 × 690
  4. Step 4: Simplify right side
    1,420.20x = 1,469,493.00
  5. Step 5: Solve for x
    x = 1,469,493.00/1,420.20
  6. Step 6: Final answer
    x = 1,034.71

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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.