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Finding the Fourth Proportional to 102.81, 141.81 and 78.21

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Solution

The fourth proportional to 102.81, 141.81 and 78.21 is: 107.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    102.81 : 141.81 = 78.21 : x
  2. Step 2: Convert to fraction form
    102.81/141.81 = 78.21/x
  3. Step 3: Cross multiply
    102.81x = 141.81 × 78.21
  4. Step 4: Simplify right side
    102.81x = 11,090.96
  5. Step 5: Solve for x
    x = 11,090.96/102.81
  6. Step 6: Final answer
    x = 107.88

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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.