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Finding the Fourth Proportional to 57.09, 78.78 and 39.60

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Solution

The fourth proportional to 57.09, 78.78 and 39.60 is: 54.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    57.09 : 78.78 = 39.60 : x
  2. Step 2: Convert to fraction form
    57.09/78.78 = 39.60/x
  3. Step 3: Cross multiply
    57.09x = 78.78 × 39.60
  4. Step 4: Simplify right side
    57.09x = 3,119.69
  5. Step 5: Solve for x
    x = 3,119.69/57.09
  6. Step 6: Final answer
    x = 54.65

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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.