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Finding the Fourth Proportional to 211.40, 316.96 and 81.40

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Solution

The fourth proportional to 211.40, 316.96 and 81.40 is: 122.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    211.40 : 316.96 = 81.40 : x
  2. Step 2: Convert to fraction form
    211.40/316.96 = 81.40/x
  3. Step 3: Cross multiply
    211.40x = 316.96 × 81.40
  4. Step 4: Simplify right side
    211.40x = 25,800.54
  5. Step 5: Solve for x
    x = 25,800.54/211.40
  6. Step 6: Final answer
    x = 122.05

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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.