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Finding the Third Proportional to 21 and 42.75

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Solution

The third proportional to 21 and 42.75 is: 87.03

Step by Step Solution

  1. Step 1: Write the proportion equation
    21 : 42.75 = 42.75 : x
  2. Step 2: Convert to fraction form
    21/42.75 = 42.75/x
  3. Step 3: Cross multiply
    21x = 42.75 × 42.75
  4. Step 4: Simplify right side
    21x = 1,827.56
  5. Step 5: Solve for x
    x = 1,827.56/21
  6. Step 6: Final answer
    x = 87.03

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Why These Related Problems?

These problems maintain the same ratio (2.04) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.