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Finding the Fourth Proportional to 1,215, 1,676.79 and 691.20

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Solution

The fourth proportional to 1,215, 1,676.79 and 691.20 is: 953.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,215 : 1,676.79 = 691.20 : x
  2. Step 2: Convert to fraction form
    1,215/1,676.79 = 691.20/x
  3. Step 3: Cross multiply
    1,215x = 1,676.79 × 691.20
  4. Step 4: Simplify right side
    1,215x = 1,158,997.25
  5. Step 5: Solve for x
    x = 1,158,997.25/1,215
  6. Step 6: Final answer
    x = 953.91

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.