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Finding the Fourth Proportional to 1,991.20, 2,987.68 and 693.60

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Solution

The fourth proportional to 1,991.20, 2,987.68 and 693.60 is: 1,040.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,991.20 : 2,987.68 = 693.60 : x
  2. Step 2: Convert to fraction form
    1,991.20/2,987.68 = 693.60/x
  3. Step 3: Cross multiply
    1,991.20x = 2,987.68 × 693.60
  4. Step 4: Simplify right side
    1,991.20x = 2,072,254.85
  5. Step 5: Solve for x
    x = 2,072,254.85/1,991.20
  6. Step 6: Final answer
    x = 1,040.71

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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.