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Finding the Fourth Proportional to 20.99, 31.36 and 18

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Solution

The fourth proportional to 20.99, 31.36 and 18 is: 26.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.99 : 31.36 = 18 : x
  2. Step 2: Convert to fraction form
    20.99/31.36 = 18/x
  3. Step 3: Cross multiply
    20.99x = 31.36 × 18
  4. Step 4: Simplify right side
    20.99x = 564.48
  5. Step 5: Solve for x
    x = 564.48/20.99
  6. Step 6: Final answer
    x = 26.89

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.