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Finding the Fourth Proportional to 31.08, 42.80 and 28.79

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Solution

The fourth proportional to 31.08, 42.80 and 28.79 is: 39.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.08 : 42.80 = 28.79 : x
  2. Step 2: Convert to fraction form
    31.08/42.80 = 28.79/x
  3. Step 3: Cross multiply
    31.08x = 42.80 × 28.79
  4. Step 4: Simplify right side
    31.08x = 1,232.01
  5. Step 5: Solve for x
    x = 1,232.01/31.08
  6. Step 6: Final answer
    x = 39.64

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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.