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Finding the Fourth Proportional to 31.20, 43.08 and 21.51

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Solution

The fourth proportional to 31.20, 43.08 and 21.51 is: 29.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.20 : 43.08 = 21.51 : x
  2. Step 2: Convert to fraction form
    31.20/43.08 = 21.51/x
  3. Step 3: Cross multiply
    31.20x = 43.08 × 21.51
  4. Step 4: Simplify right side
    31.20x = 926.65
  5. Step 5: Solve for x
    x = 926.65/31.20
  6. Step 6: Final answer
    x = 29.70

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.