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Finding the Fourth Proportional to 839.62, 1,259.40 and 428.74

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Solution

The fourth proportional to 839.62, 1,259.40 and 428.74 is: 643.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    839.62 : 1,259.40 = 428.74 : x
  2. Step 2: Convert to fraction form
    839.62/1,259.40 = 428.74/x
  3. Step 3: Cross multiply
    839.62x = 1,259.40 × 428.74
  4. Step 4: Simplify right side
    839.62x = 539,958.29
  5. Step 5: Solve for x
    x = 539,958.29/839.62
  6. Step 6: Final answer
    x = 643.10

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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.