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Finding the Fourth Proportional to 99.70, 137.45 and 85.78

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Solution

The fourth proportional to 99.70, 137.45 and 85.78 is: 118.26

Step by Step Solution

  1. Step 1: Write the proportion equation
    99.70 : 137.45 = 85.78 : x
  2. Step 2: Convert to fraction form
    99.70/137.45 = 85.78/x
  3. Step 3: Cross multiply
    99.70x = 137.45 × 85.78
  4. Step 4: Simplify right side
    99.70x = 11,790.46
  5. Step 5: Solve for x
    x = 11,790.46/99.70
  6. Step 6: Final answer
    x = 118.26

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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.