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Finding the Fourth Proportional to 780.80, 1,079.04 and 640.70

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Solution

The fourth proportional to 780.80, 1,079.04 and 640.70 is: 885.43

Step by Step Solution

  1. Step 1: Write the proportion equation
    780.80 : 1,079.04 = 640.70 : x
  2. Step 2: Convert to fraction form
    780.80/1,079.04 = 640.70/x
  3. Step 3: Cross multiply
    780.80x = 1,079.04 × 640.70
  4. Step 4: Simplify right side
    780.80x = 691,340.93
  5. Step 5: Solve for x
    x = 691,340.93/780.80
  6. Step 6: Final answer
    x = 885.43

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.