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Finding the Fourth Proportional to 640.50, 961.20 and 421.11

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Solution

The fourth proportional to 640.50, 961.20 and 421.11 is: 631.96

Step by Step Solution

  1. Step 1: Write the proportion equation
    640.50 : 961.20 = 421.11 : x
  2. Step 2: Convert to fraction form
    640.50/961.20 = 421.11/x
  3. Step 3: Cross multiply
    640.50x = 961.20 × 421.11
  4. Step 4: Simplify right side
    640.50x = 404,770.93
  5. Step 5: Solve for x
    x = 404,770.93/640.50
  6. Step 6: Final answer
    x = 631.96

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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.