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Finding the Fourth Proportional to 91.70, 136.80 and 81

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Solution

The fourth proportional to 91.70, 136.80 and 81 is: 120.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.70 : 136.80 = 81 : x
  2. Step 2: Convert to fraction form
    91.70/136.80 = 81/x
  3. Step 3: Cross multiply
    91.70x = 136.80 × 81
  4. Step 4: Simplify right side
    91.70x = 11,080.80
  5. Step 5: Solve for x
    x = 11,080.80/91.70
  6. Step 6: Final answer
    x = 120.84

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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.