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Finding the Fourth Proportional to 312.78, 431.64 and 172.90

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Solution

The fourth proportional to 312.78, 431.64 and 172.90 is: 238.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    312.78 : 431.64 = 172.90 : x
  2. Step 2: Convert to fraction form
    312.78/431.64 = 172.90/x
  3. Step 3: Cross multiply
    312.78x = 431.64 × 172.90
  4. Step 4: Simplify right side
    312.78x = 74,628.72
  5. Step 5: Solve for x
    x = 74,628.72/312.78
  6. Step 6: Final answer
    x = 238.60

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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.