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Finding the Third Proportional to 687 and 990

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Solution

The third proportional to 687 and 990 is: 1,426.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    687 : 990 = 990 : x
  2. Step 2: Convert to fraction form
    687/990 = 990/x
  3. Step 3: Cross multiply
    687x = 990 × 990
  4. Step 4: Simplify right side
    687x = 980,100
  5. Step 5: Solve for x
    x = 980,100/687
  6. Step 6: Final answer
    x = 1,426.64

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Why These Related Problems?

These problems maintain the same ratio (1.44) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.