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Finding the Fourth Proportional to 20.79, 31.20 and 18.51

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Solution

The fourth proportional to 20.79, 31.20 and 18.51 is: 27.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.79 : 31.20 = 18.51 : x
  2. Step 2: Convert to fraction form
    20.79/31.20 = 18.51/x
  3. Step 3: Cross multiply
    20.79x = 31.20 × 18.51
  4. Step 4: Simplify right side
    20.79x = 577.51
  5. Step 5: Solve for x
    x = 577.51/20.79
  6. Step 6: Final answer
    x = 27.78

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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.