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Finding the Fourth Proportional to 21.36, 31.86 and 18

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Solution

The fourth proportional to 21.36, 31.86 and 18 is: 26.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.36 : 31.86 = 18 : x
  2. Step 2: Convert to fraction form
    21.36/31.86 = 18/x
  3. Step 3: Cross multiply
    21.36x = 31.86 × 18
  4. Step 4: Simplify right side
    21.36x = 573.48
  5. Step 5: Solve for x
    x = 573.48/21.36
  6. Step 6: Final answer
    x = 26.85

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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.