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Finding the Fourth Proportional to 87.90, 121.40 and 66.16

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Solution

The fourth proportional to 87.90, 121.40 and 66.16 is: 91.37

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.90 : 121.40 = 66.16 : x
  2. Step 2: Convert to fraction form
    87.90/121.40 = 66.16/x
  3. Step 3: Cross multiply
    87.90x = 121.40 × 66.16
  4. Step 4: Simplify right side
    87.90x = 8,031.82
  5. Step 5: Solve for x
    x = 8,031.82/87.90
  6. Step 6: Final answer
    x = 91.37

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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.