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Finding the Fourth Proportional to 1,987.74, 2,979.72 and 891

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Solution

The fourth proportional to 1,987.74, 2,979.72 and 891 is: 1,335.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,987.74 : 2,979.72 = 891 : x
  2. Step 2: Convert to fraction form
    1,987.74/2,979.72 = 891/x
  3. Step 3: Cross multiply
    1,987.74x = 2,979.72 × 891
  4. Step 4: Simplify right side
    1,987.74x = 2,654,930.52
  5. Step 5: Solve for x
    x = 2,654,930.52/1,987.74
  6. Step 6: Final answer
    x = 1,335.65

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.