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Finding the Fourth Proportional to 31.12, 42.91 and 20.77

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Solution

The fourth proportional to 31.12, 42.91 and 20.77 is: 28.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.12 : 42.91 = 20.77 : x
  2. Step 2: Convert to fraction form
    31.12/42.91 = 20.77/x
  3. Step 3: Cross multiply
    31.12x = 42.91 × 20.77
  4. Step 4: Simplify right side
    31.12x = 891.24
  5. Step 5: Solve for x
    x = 891.24/31.12
  6. Step 6: Final answer
    x = 28.64

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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.