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Finding the Fourth Proportional to 102.90, 141.72 and 78.30

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Solution

The fourth proportional to 102.90, 141.72 and 78.30 is: 107.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    102.90 : 141.72 = 78.30 : x
  2. Step 2: Convert to fraction form
    102.90/141.72 = 78.30/x
  3. Step 3: Cross multiply
    102.90x = 141.72 × 78.30
  4. Step 4: Simplify right side
    102.90x = 11,096.68
  5. Step 5: Solve for x
    x = 11,096.68/102.90
  6. Step 6: Final answer
    x = 107.84

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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.