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Finding the Fourth Proportional to 78.12, 107.78 and 47

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Solution

The fourth proportional to 78.12, 107.78 and 47 is: 64.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.12 : 107.78 = 47 : x
  2. Step 2: Convert to fraction form
    78.12/107.78 = 47/x
  3. Step 3: Cross multiply
    78.12x = 107.78 × 47
  4. Step 4: Simplify right side
    78.12x = 5,065.66
  5. Step 5: Solve for x
    x = 5,065.66/78.12
  6. Step 6: Final answer
    x = 64.84

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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.