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Finding the Fourth Proportional to 1,287, 1,774.86 and 991.80

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Solution

The fourth proportional to 1,287, 1,774.86 and 991.80 is: 1,367.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,287 : 1,774.86 = 991.80 : x
  2. Step 2: Convert to fraction form
    1,287/1,774.86 = 991.80/x
  3. Step 3: Cross multiply
    1,287x = 1,774.86 × 991.80
  4. Step 4: Simplify right side
    1,287x = 1,760,306.15
  5. Step 5: Solve for x
    x = 1,760,306.15/1,287
  6. Step 6: Final answer
    x = 1,367.76

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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.