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Finding the Third Proportional to 421 and 640

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Solution

The third proportional to 421 and 640 is: 972.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    421 : 640 = 640 : x
  2. Step 2: Convert to fraction form
    421/640 = 640/x
  3. Step 3: Cross multiply
    421x = 640 × 640
  4. Step 4: Simplify right side
    421x = 409,600
  5. Step 5: Solve for x
    x = 409,600/421
  6. Step 6: Final answer
    x = 972.92

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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.