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Finding the Third Proportional to 420.75 and 644.63

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Solution

The third proportional to 420.75 and 644.63 is: 987.62

Step by Step Solution

  1. Step 1: Write the proportion equation
    420.75 : 644.63 = 644.63 : x
  2. Step 2: Convert to fraction form
    420.75/644.63 = 644.63/x
  3. Step 3: Cross multiply
    420.75x = 644.63 × 644.63
  4. Step 4: Simplify right side
    420.75x = 415,541.39
  5. Step 5: Solve for x
    x = 415,541.39/420.75
  6. Step 6: Final answer
    x = 987.62

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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.