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Finding the Fourth Proportional to 78.51, 108.21 and 68.79

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Solution

The fourth proportional to 78.51, 108.21 and 68.79 is: 94.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.51 : 108.21 = 68.79 : x
  2. Step 2: Convert to fraction form
    78.51/108.21 = 68.79/x
  3. Step 3: Cross multiply
    78.51x = 108.21 × 68.79
  4. Step 4: Simplify right side
    78.51x = 7,443.77
  5. Step 5: Solve for x
    x = 7,443.77/78.51
  6. Step 6: Final answer
    x = 94.81

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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.