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Finding the Third Proportional to 421.50 and 643

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Solution

The third proportional to 421.50 and 643 is: 980.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    421.50 : 643 = 643 : x
  2. Step 2: Convert to fraction form
    421.50/643 = 643/x
  3. Step 3: Cross multiply
    421.50x = 643 × 643
  4. Step 4: Simplify right side
    421.50x = 413,449
  5. Step 5: Solve for x
    x = 413,449/421.50
  6. Step 6: Final answer
    x = 980.90

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Why These Related Problems?

These problems maintain the same ratio (1.53) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.