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Finding the Fourth Proportional to 99.78, 137.74 and 66.63

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Solution

The fourth proportional to 99.78, 137.74 and 66.63 is: 91.99

Step by Step Solution

  1. Step 1: Write the proportion equation
    99.78 : 137.74 = 66.63 : x
  2. Step 2: Convert to fraction form
    99.78/137.74 = 66.63/x
  3. Step 3: Cross multiply
    99.78x = 137.74 × 66.63
  4. Step 4: Simplify right side
    99.78x = 9,177.97
  5. Step 5: Solve for x
    x = 9,177.97/99.78
  6. Step 6: Final answer
    x = 91.99

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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.