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Finding the Fourth Proportional to 781.75, 1,078.70 and 664.20

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Solution

The fourth proportional to 781.75, 1,078.70 and 664.20 is: 916.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.75 : 1,078.70 = 664.20 : x
  2. Step 2: Convert to fraction form
    781.75/1,078.70 = 664.20/x
  3. Step 3: Cross multiply
    781.75x = 1,078.70 × 664.20
  4. Step 4: Simplify right side
    781.75x = 716,467.15
  5. Step 5: Solve for x
    x = 716,467.15/781.75
  6. Step 6: Final answer
    x = 916.49

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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.