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Finding the Fourth Proportional to 1,387.70, 2,080.05 and 770.78

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Solution

The fourth proportional to 1,387.70, 2,080.05 and 770.78 is: 1,155.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,387.70 : 2,080.05 = 770.78 : x
  2. Step 2: Convert to fraction form
    1,387.70/2,080.05 = 770.78/x
  3. Step 3: Cross multiply
    1,387.70x = 2,080.05 × 770.78
  4. Step 4: Simplify right side
    1,387.70x = 1,603,260.94
  5. Step 5: Solve for x
    x = 1,603,260.94/1,387.70
  6. Step 6: Final answer
    x = 1,155.34

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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.