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Finding the Fourth Proportional to 1,321.25, 1,979.74 and 860.15

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Solution

The fourth proportional to 1,321.25, 1,979.74 and 860.15 is: 1,288.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,321.25 : 1,979.74 = 860.15 : x
  2. Step 2: Convert to fraction form
    1,321.25/1,979.74 = 860.15/x
  3. Step 3: Cross multiply
    1,321.25x = 1,979.74 × 860.15
  4. Step 4: Simplify right side
    1,321.25x = 1,702,879.39
  5. Step 5: Solve for x
    x = 1,702,879.39/1,321.25
  6. Step 6: Final answer
    x = 1,288.84

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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.