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Finding the Fourth Proportional to 21, 31.49 and 18

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Solution

The fourth proportional to 21, 31.49 and 18 is: 26.99

Step by Step Solution

  1. Step 1: Write the proportion equation
    21 : 31.49 = 18 : x
  2. Step 2: Convert to fraction form
    21/31.49 = 18/x
  3. Step 3: Cross multiply
    21x = 31.49 × 18
  4. Step 4: Simplify right side
    21x = 566.73
  5. Step 5: Solve for x
    x = 566.73/21
  6. Step 6: Final answer
    x = 26.99

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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.