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Finding the Fourth Proportional to 2,078.80, 3,119.40 and 781.20

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Solution

The fourth proportional to 2,078.80, 3,119.40 and 781.20 is: 1,172.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    2,078.80 : 3,119.40 = 781.20 : x
  2. Step 2: Convert to fraction form
    2,078.80/3,119.40 = 781.20/x
  3. Step 3: Cross multiply
    2,078.80x = 3,119.40 × 781.20
  4. Step 4: Simplify right side
    2,078.80x = 2,436,875.28
  5. Step 5: Solve for x
    x = 2,436,875.28/2,078.80
  6. Step 6: Final answer
    x = 1,172.25

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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.