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Finding the Fourth Proportional to 781.80, 1,080.42 and 641.70

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Solution

The fourth proportional to 781.80, 1,080.42 and 641.70 is: 886.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.80 : 1,080.42 = 641.70 : x
  2. Step 2: Convert to fraction form
    781.80/1,080.42 = 641.70/x
  3. Step 3: Cross multiply
    781.80x = 1,080.42 × 641.70
  4. Step 4: Simplify right side
    781.80x = 693,305.51
  5. Step 5: Solve for x
    x = 693,305.51/781.80
  6. Step 6: Final answer
    x = 886.81

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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.