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Finding the Fourth Proportional to 689.87, 1,029.78 and 639.18

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Solution

The fourth proportional to 689.87, 1,029.78 and 639.18 is: 954.11

Step by Step Solution

  1. Step 1: Write the proportion equation
    689.87 : 1,029.78 = 639.18 : x
  2. Step 2: Convert to fraction form
    689.87/1,029.78 = 639.18/x
  3. Step 3: Cross multiply
    689.87x = 1,029.78 × 639.18
  4. Step 4: Simplify right side
    689.87x = 658,214.78
  5. Step 5: Solve for x
    x = 658,214.78/689.87
  6. Step 6: Final answer
    x = 954.11

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.