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Finding the Fourth Proportional to 828.40, 1,239.90 and 644.80

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Solution

The fourth proportional to 828.40, 1,239.90 and 644.80 is: 965.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    828.40 : 1,239.90 = 644.80 : x
  2. Step 2: Convert to fraction form
    828.40/1,239.90 = 644.80/x
  3. Step 3: Cross multiply
    828.40x = 1,239.90 × 644.80
  4. Step 4: Simplify right side
    828.40x = 799,487.52
  5. Step 5: Solve for x
    x = 799,487.52/828.40
  6. Step 6: Final answer
    x = 965.10

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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.