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Finding the Fourth Proportional to 90.80, 135.46 and 85.72

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Solution

The fourth proportional to 90.80, 135.46 and 85.72 is: 127.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.80 : 135.46 = 85.72 : x
  2. Step 2: Convert to fraction form
    90.80/135.46 = 85.72/x
  3. Step 3: Cross multiply
    90.80x = 135.46 × 85.72
  4. Step 4: Simplify right side
    90.80x = 11,611.63
  5. Step 5: Solve for x
    x = 11,611.63/90.80
  6. Step 6: Final answer
    x = 127.88

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.