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Finding the Fourth Proportional to 1,272.80, 1,909.20 and 778.70

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Solution

The fourth proportional to 1,272.80, 1,909.20 and 778.70 is: 1,168.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,272.80 : 1,909.20 = 778.70 : x
  2. Step 2: Convert to fraction form
    1,272.80/1,909.20 = 778.70/x
  3. Step 3: Cross multiply
    1,272.80x = 1,909.20 × 778.70
  4. Step 4: Simplify right side
    1,272.80x = 1,486,694.04
  5. Step 5: Solve for x
    x = 1,486,694.04/1,272.80
  6. Step 6: Final answer
    x = 1,168.05

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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.