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Finding the Fourth Proportional to 428.75, 643.13 and 172.43

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Solution

The fourth proportional to 428.75, 643.13 and 172.43 is: 258.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.75 : 643.13 = 172.43 : x
  2. Step 2: Convert to fraction form
    428.75/643.13 = 172.43/x
  3. Step 3: Cross multiply
    428.75x = 643.13 × 172.43
  4. Step 4: Simplify right side
    428.75x = 110,894.91
  5. Step 5: Solve for x
    x = 110,894.91/428.75
  6. Step 6: Final answer
    x = 258.65

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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.