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Finding the Fourth Proportional to 77.85, 107.40 and 57.15

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Solution

The fourth proportional to 77.85, 107.40 and 57.15 is: 78.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    77.85 : 107.40 = 57.15 : x
  2. Step 2: Convert to fraction form
    77.85/107.40 = 57.15/x
  3. Step 3: Cross multiply
    77.85x = 107.40 × 57.15
  4. Step 4: Simplify right side
    77.85x = 6,137.91
  5. Step 5: Solve for x
    x = 6,137.91/77.85
  6. Step 6: Final answer
    x = 78.84

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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.