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Finding the Fourth Proportional to 985.80, 1,479.90 and 978.60

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Solution

The fourth proportional to 985.80, 1,479.90 and 978.60 is: 1,469.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    985.80 : 1,479.90 = 978.60 : x
  2. Step 2: Convert to fraction form
    985.80/1,479.90 = 978.60/x
  3. Step 3: Cross multiply
    985.80x = 1,479.90 × 978.60
  4. Step 4: Simplify right side
    985.80x = 1,448,230.14
  5. Step 5: Solve for x
    x = 1,448,230.14/985.80
  6. Step 6: Final answer
    x = 1,469.09

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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.