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Finding the Fourth Proportional to 1,287.40, 1,928.56 and 786.28

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Solution

The fourth proportional to 1,287.40, 1,928.56 and 786.28 is: 1,177.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,287.40 : 1,928.56 = 786.28 : x
  2. Step 2: Convert to fraction form
    1,287.40/1,928.56 = 786.28/x
  3. Step 3: Cross multiply
    1,287.40x = 1,928.56 × 786.28
  4. Step 4: Simplify right side
    1,287.40x = 1,516,388.16
  5. Step 5: Solve for x
    x = 1,516,388.16/1,287.40
  6. Step 6: Final answer
    x = 1,177.87

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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.