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Finding the Fourth Proportional to 81.40, 121.90 and 47.05

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Solution

The fourth proportional to 81.40, 121.90 and 47.05 is: 70.47

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.40 : 121.90 = 47.05 : x
  2. Step 2: Convert to fraction form
    81.40/121.90 = 47.05/x
  3. Step 3: Cross multiply
    81.40x = 121.90 × 47.05
  4. Step 4: Simplify right side
    81.40x = 5,735.66
  5. Step 5: Solve for x
    x = 5,735.66/81.40
  6. Step 6: Final answer
    x = 70.47

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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.