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Finding the Fourth Proportional to 77.20, 115.72 and 31.51

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Solution

The fourth proportional to 77.20, 115.72 and 31.51 is: 47.23

Step by Step Solution

  1. Step 1: Write the proportion equation
    77.20 : 115.72 = 31.51 : x
  2. Step 2: Convert to fraction form
    77.20/115.72 = 31.51/x
  3. Step 3: Cross multiply
    77.20x = 115.72 × 31.51
  4. Step 4: Simplify right side
    77.20x = 3,646.34
  5. Step 5: Solve for x
    x = 3,646.34/77.20
  6. Step 6: Final answer
    x = 47.23

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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.