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Finding the Fourth Proportional to 121.51, 182.31 and 85.78

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Solution

The fourth proportional to 121.51, 182.31 and 85.78 is: 128.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    121.51 : 182.31 = 85.78 : x
  2. Step 2: Convert to fraction form
    121.51/182.31 = 85.78/x
  3. Step 3: Cross multiply
    121.51x = 182.31 × 85.78
  4. Step 4: Simplify right side
    121.51x = 15,638.55
  5. Step 5: Solve for x
    x = 15,638.55/121.51
  6. Step 6: Final answer
    x = 128.70

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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.