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Finding the Fourth Proportional to 102.78, 141.71 and 87.21

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Solution

The fourth proportional to 102.78, 141.71 and 87.21 is: 120.24

Step by Step Solution

  1. Step 1: Write the proportion equation
    102.78 : 141.71 = 87.21 : x
  2. Step 2: Convert to fraction form
    102.78/141.71 = 87.21/x
  3. Step 3: Cross multiply
    102.78x = 141.71 × 87.21
  4. Step 4: Simplify right side
    102.78x = 12,358.09
  5. Step 5: Solve for x
    x = 12,358.09/102.78
  6. Step 6: Final answer
    x = 120.24

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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.