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Finding the Third Proportional to 870 and 1,991

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Solution

The third proportional to 870 and 1,991 is: 4,556.41

Step by Step Solution

  1. Step 1: Write the proportion equation
    870 : 1,991 = 1,991 : x
  2. Step 2: Convert to fraction form
    870/1,991 = 1,991/x
  3. Step 3: Cross multiply
    870x = 1,991 × 1,991
  4. Step 4: Simplify right side
    870x = 3,964,081
  5. Step 5: Solve for x
    x = 3,964,081/870
  6. Step 6: Final answer
    x = 4,556.41

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Why These Related Problems?

These problems maintain the same ratio (2.29) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.