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Finding the Fourth Proportional to 209.30, 313.49 and 128.21

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Solution

The fourth proportional to 209.30, 313.49 and 128.21 is: 192.03

Step by Step Solution

  1. Step 1: Write the proportion equation
    209.30 : 313.49 = 128.21 : x
  2. Step 2: Convert to fraction form
    209.30/313.49 = 128.21/x
  3. Step 3: Cross multiply
    209.30x = 313.49 × 128.21
  4. Step 4: Simplify right side
    209.30x = 40,191.31
  5. Step 5: Solve for x
    x = 40,191.31/209.30
  6. Step 6: Final answer
    x = 192.03

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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.