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Finding the Fourth Proportional to 1,687.20, 2,328.18 and 978.90

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Solution

The fourth proportional to 1,687.20, 2,328.18 and 978.90 is: 1,350.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,687.20 : 2,328.18 = 978.90 : x
  2. Step 2: Convert to fraction form
    1,687.20/2,328.18 = 978.90/x
  3. Step 3: Cross multiply
    1,687.20x = 2,328.18 × 978.90
  4. Step 4: Simplify right side
    1,687.20x = 2,279,055.40
  5. Step 5: Solve for x
    x = 2,279,055.40/1,687.20
  6. Step 6: Final answer
    x = 1,350.79

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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.