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Finding the Fourth Proportional to 212.70, 318.78 and 90.90

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Solution

The fourth proportional to 212.70, 318.78 and 90.90 is: 136.23

Step by Step Solution

  1. Step 1: Write the proportion equation
    212.70 : 318.78 = 90.90 : x
  2. Step 2: Convert to fraction form
    212.70/318.78 = 90.90/x
  3. Step 3: Cross multiply
    212.70x = 318.78 × 90.90
  4. Step 4: Simplify right side
    212.70x = 28,977.10
  5. Step 5: Solve for x
    x = 28,977.10/212.70
  6. Step 6: Final answer
    x = 136.23

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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.