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Finding the Fourth Proportional to 85.62, 128.39 and 31.51

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Solution

The fourth proportional to 85.62, 128.39 and 31.51 is: 47.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.62 : 128.39 = 31.51 : x
  2. Step 2: Convert to fraction form
    85.62/128.39 = 31.51/x
  3. Step 3: Cross multiply
    85.62x = 128.39 × 31.51
  4. Step 4: Simplify right side
    85.62x = 4,045.57
  5. Step 5: Solve for x
    x = 4,045.57/85.62
  6. Step 6: Final answer
    x = 47.25

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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.