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Finding the Third Proportional to 319.78 and 690.61

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Solution

The third proportional to 319.78 and 690.61 is: 1,491.46

Step by Step Solution

  1. Step 1: Write the proportion equation
    319.78 : 690.61 = 690.61 : x
  2. Step 2: Convert to fraction form
    319.78/690.61 = 690.61/x
  3. Step 3: Cross multiply
    319.78x = 690.61 × 690.61
  4. Step 4: Simplify right side
    319.78x = 476,941.31
  5. Step 5: Solve for x
    x = 476,941.31/319.78
  6. Step 6: Final answer
    x = 1,491.46

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Why These Related Problems?

These problems maintain the same ratio (2.16) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.