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Finding the Third Proportional to 915 and 1,221

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Solution

The third proportional to 915 and 1,221 is: 1,629.33

Step by Step Solution

  1. Step 1: Write the proportion equation
    915 : 1,221 = 1,221 : x
  2. Step 2: Convert to fraction form
    915/1,221 = 1,221/x
  3. Step 3: Cross multiply
    915x = 1,221 × 1,221
  4. Step 4: Simplify right side
    915x = 1,490,841
  5. Step 5: Solve for x
    x = 1,490,841/915
  6. Step 6: Final answer
    x = 1,629.33

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Why These Related Problems?

These problems maintain the same ratio (1.33) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.