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Finding the Fourth Proportional to 87.28, 120.64 and 84.21

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Solution

The fourth proportional to 87.28, 120.64 and 84.21 is: 116.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.28 : 120.64 = 84.21 : x
  2. Step 2: Convert to fraction form
    87.28/120.64 = 84.21/x
  3. Step 3: Cross multiply
    87.28x = 120.64 × 84.21
  4. Step 4: Simplify right side
    87.28x = 10,159.09
  5. Step 5: Solve for x
    x = 10,159.09/87.28
  6. Step 6: Final answer
    x = 116.40

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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.