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Finding the Fourth Proportional to 342.31, 513.47 and 85.81

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Solution

The fourth proportional to 342.31, 513.47 and 85.81 is: 128.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    342.31 : 513.47 = 85.81 : x
  2. Step 2: Convert to fraction form
    342.31/513.47 = 85.81/x
  3. Step 3: Cross multiply
    342.31x = 513.47 × 85.81
  4. Step 4: Simplify right side
    342.31x = 44,060.86
  5. Step 5: Solve for x
    x = 44,060.86/342.31
  6. Step 6: Final answer
    x = 128.72

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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.