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Finding the Fourth Proportional to 7,240, 9,991.20 and 3,928

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Solution

The fourth proportional to 7,240, 9,991.20 and 3,928 is: 5,420.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    7,240 : 9,991.20 = 3,928 : x
  2. Step 2: Convert to fraction form
    7,240/9,991.20 = 3,928/x
  3. Step 3: Cross multiply
    7,240x = 9,991.20 × 3,928
  4. Step 4: Simplify right side
    7,240x = 39,245,433.60
  5. Step 5: Solve for x
    x = 39,245,433.60/7,240
  6. Step 6: Final answer
    x = 5,420.64

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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.