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Finding the Fourth Proportional to 87.84, 121.14 and 78.60

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Solution

The fourth proportional to 87.84, 121.14 and 78.60 is: 108.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.84 : 121.14 = 78.60 : x
  2. Step 2: Convert to fraction form
    87.84/121.14 = 78.60/x
  3. Step 3: Cross multiply
    87.84x = 121.14 × 78.60
  4. Step 4: Simplify right side
    87.84x = 9,521.60
  5. Step 5: Solve for x
    x = 9,521.60/87.84
  6. Step 6: Final answer
    x = 108.40

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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.