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Finding the Fourth Proportional to 102.90, 142.05 and 76.70

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Solution

The fourth proportional to 102.90, 142.05 and 76.70 is: 105.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    102.90 : 142.05 = 76.70 : x
  2. Step 2: Convert to fraction form
    102.90/142.05 = 76.70/x
  3. Step 3: Cross multiply
    102.90x = 142.05 × 76.70
  4. Step 4: Simplify right side
    102.90x = 10,895.08
  5. Step 5: Solve for x
    x = 10,895.08/102.90
  6. Step 6: Final answer
    x = 105.89

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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.