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Finding the Fourth Proportional to 81.12, 121.50 and 45

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Solution

The fourth proportional to 81.12, 121.50 and 45 is: 67.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.12 : 121.50 = 45 : x
  2. Step 2: Convert to fraction form
    81.12/121.50 = 45/x
  3. Step 3: Cross multiply
    81.12x = 121.50 × 45
  4. Step 4: Simplify right side
    81.12x = 5,467.50
  5. Step 5: Solve for x
    x = 5,467.50/81.12
  6. Step 6: Final answer
    x = 67.40

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.