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Finding the Fourth Proportional to 103.40, 142.40 and 78.80

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Solution

The fourth proportional to 103.40, 142.40 and 78.80 is: 108.52

Step by Step Solution

  1. Step 1: Write the proportion equation
    103.40 : 142.40 = 78.80 : x
  2. Step 2: Convert to fraction form
    103.40/142.40 = 78.80/x
  3. Step 3: Cross multiply
    103.40x = 142.40 × 78.80
  4. Step 4: Simplify right side
    103.40x = 11,221.12
  5. Step 5: Solve for x
    x = 11,221.12/103.40
  6. Step 6: Final answer
    x = 108.52

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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.