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Finding the Third Proportional to 421.88 and 640.13

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Solution

The third proportional to 421.88 and 640.13 is: 971.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    421.88 : 640.13 = 640.13 : x
  2. Step 2: Convert to fraction form
    421.88/640.13 = 640.13/x
  3. Step 3: Cross multiply
    421.88x = 640.13 × 640.13
  4. Step 4: Simplify right side
    421.88x = 409,760.02
  5. Step 5: Solve for x
    x = 409,760.02/421.88
  6. Step 6: Final answer
    x = 971.28

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Why These Related Problems?

These problems maintain the same ratio (1.52) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.