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Finding the Fourth Proportional to 2,139.70, 3,209.55 and 987.70

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Solution

The fourth proportional to 2,139.70, 3,209.55 and 987.70 is: 1,481.55

Step by Step Solution

  1. Step 1: Write the proportion equation
    2,139.70 : 3,209.55 = 987.70 : x
  2. Step 2: Convert to fraction form
    2,139.70/3,209.55 = 987.70/x
  3. Step 3: Cross multiply
    2,139.70x = 3,209.55 × 987.70
  4. Step 4: Simplify right side
    2,139.70x = 3,170,072.54
  5. Step 5: Solve for x
    x = 3,170,072.54/2,139.70
  6. Step 6: Final answer
    x = 1,481.55

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1.5x scale

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.