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Finding the Fourth Proportional to 172.40, 258.42 and 85.64

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Solution

The fourth proportional to 172.40, 258.42 and 85.64 is: 128.37

Step by Step Solution

  1. Step 1: Write the proportion equation
    172.40 : 258.42 = 85.64 : x
  2. Step 2: Convert to fraction form
    172.40/258.42 = 85.64/x
  3. Step 3: Cross multiply
    172.40x = 258.42 × 85.64
  4. Step 4: Simplify right side
    172.40x = 22,131.09
  5. Step 5: Solve for x
    x = 22,131.09/172.40
  6. Step 6: Final answer
    x = 128.37

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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.