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Finding the Fourth Proportional to 859.20, 1,289.20 and 643.20

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Solution

The fourth proportional to 859.20, 1,289.20 and 643.20 is: 965.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    859.20 : 1,289.20 = 643.20 : x
  2. Step 2: Convert to fraction form
    859.20/1,289.20 = 643.20/x
  3. Step 3: Cross multiply
    859.20x = 1,289.20 × 643.20
  4. Step 4: Simplify right side
    859.20x = 829,213.44
  5. Step 5: Solve for x
    x = 829,213.44/859.20
  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.