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Finding the Fourth Proportional to 1,280.40, 1,768.40 and 989.20

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Solution

The fourth proportional to 1,280.40, 1,768.40 and 989.20 is: 1,366.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,280.40 : 1,768.40 = 989.20 : x
  2. Step 2: Convert to fraction form
    1,280.40/1,768.40 = 989.20/x
  3. Step 3: Cross multiply
    1,280.40x = 1,768.40 × 989.20
  4. Step 4: Simplify right side
    1,280.40x = 1,749,301.28
  5. Step 5: Solve for x
    x = 1,749,301.28/1,280.40
  6. Step 6: Final answer
    x = 1,366.21

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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.