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Finding the Fourth Proportional to 1,215.78, 1,677.90 and 691.75

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Solution

The fourth proportional to 1,215.78, 1,677.90 and 691.75 is: 954.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,215.78 : 1,677.90 = 691.75 : x
  2. Step 2: Convert to fraction form
    1,215.78/1,677.90 = 691.75/x
  3. Step 3: Cross multiply
    1,215.78x = 1,677.90 × 691.75
  4. Step 4: Simplify right side
    1,215.78x = 1,160,687.33
  5. Step 5: Solve for x
    x = 1,160,687.33/1,215.78
  6. Step 6: Final answer
    x = 954.69

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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.