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Finding the Fourth Proportional to 428.80, 642.72 and 172

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Solution

The fourth proportional to 428.80, 642.72 and 172 is: 257.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.80 : 642.72 = 172 : x
  2. Step 2: Convert to fraction form
    428.80/642.72 = 172/x
  3. Step 3: Cross multiply
    428.80x = 642.72 × 172
  4. Step 4: Simplify right side
    428.80x = 110,547.84
  5. Step 5: Solve for x
    x = 110,547.84/428.80
  6. Step 6: Final answer
    x = 257.81

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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.