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Finding the Fourth Proportional to 99.75, 137.61 and 64.78

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Solution

The fourth proportional to 99.75, 137.61 and 64.78 is: 89.36

Step by Step Solution

  1. Step 1: Write the proportion equation
    99.75 : 137.61 = 64.78 : x
  2. Step 2: Convert to fraction form
    99.75/137.61 = 64.78/x
  3. Step 3: Cross multiply
    99.75x = 137.61 × 64.78
  4. Step 4: Simplify right side
    99.75x = 8,914.03
  5. Step 5: Solve for x
    x = 8,914.03/99.75
  6. Step 6: Final answer
    x = 89.36

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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.