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Finding the Fourth Proportional to 312.78, 431.61 and 172.89

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Solution

The fourth proportional to 312.78, 431.61 and 172.89 is: 238.57

Step by Step Solution

  1. Step 1: Write the proportion equation
    312.78 : 431.61 = 172.89 : x
  2. Step 2: Convert to fraction form
    312.78/431.61 = 172.89/x
  3. Step 3: Cross multiply
    312.78x = 431.61 × 172.89
  4. Step 4: Simplify right side
    312.78x = 74,621.05
  5. Step 5: Solve for x
    x = 74,621.05/312.78
  6. Step 6: Final answer
    x = 238.57

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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.