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Finding the Fourth Proportional to 805.21, 1,207.80 and 643.91

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Solution

The fourth proportional to 805.21, 1,207.80 and 643.91 is: 965.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    805.21 : 1,207.80 = 643.91 : x
  2. Step 2: Convert to fraction form
    805.21/1,207.80 = 643.91/x
  3. Step 3: Cross multiply
    805.21x = 1,207.80 × 643.91
  4. Step 4: Simplify right side
    805.21x = 777,708.46
  5. Step 5: Solve for x
    x = 777,708.46/805.21
  6. Step 6: Final answer
    x = 965.85

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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.