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Finding the Fourth Proportional to 39.72, 54.90 and 31.08

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Solution

The fourth proportional to 39.72, 54.90 and 31.08 is: 42.96

Step by Step Solution

  1. Step 1: Write the proportion equation
    39.72 : 54.90 = 31.08 : x
  2. Step 2: Convert to fraction form
    39.72/54.90 = 31.08/x
  3. Step 3: Cross multiply
    39.72x = 54.90 × 31.08
  4. Step 4: Simplify right side
    39.72x = 1,706.29
  5. Step 5: Solve for x
    x = 1,706.29/39.72
  6. Step 6: Final answer
    x = 42.96

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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.