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Finding the Fourth Proportional to 1,191.87, 1,643.19 and 978.39

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Solution

The fourth proportional to 1,191.87, 1,643.19 and 978.39 is: 1,348.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,191.87 : 1,643.19 = 978.39 : x
  2. Step 2: Convert to fraction form
    1,191.87/1,643.19 = 978.39/x
  3. Step 3: Cross multiply
    1,191.87x = 1,643.19 × 978.39
  4. Step 4: Simplify right side
    1,191.87x = 1,607,680.66
  5. Step 5: Solve for x
    x = 1,607,680.66/1,191.87
  6. Step 6: Final answer
    x = 1,348.87

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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.