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Finding the Fourth Proportional to 978.80, 1,468.20 and 687.20

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Solution

The fourth proportional to 978.80, 1,468.20 and 687.20 is: 1,030.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    978.80 : 1,468.20 = 687.20 : x
  2. Step 2: Convert to fraction form
    978.80/1,468.20 = 687.20/x
  3. Step 3: Cross multiply
    978.80x = 1,468.20 × 687.20
  4. Step 4: Simplify right side
    978.80x = 1,008,947.04
  5. Step 5: Solve for x
    x = 1,008,947.04/978.80
  6. Step 6: Final answer
    x = 1,030.80

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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.