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Finding the Fourth Proportional to 209.78, 313.98 and 128.24

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Solution

The fourth proportional to 209.78, 313.98 and 128.24 is: 191.94

Step by Step Solution

  1. Step 1: Write the proportion equation
    209.78 : 313.98 = 128.24 : x
  2. Step 2: Convert to fraction form
    209.78/313.98 = 128.24/x
  3. Step 3: Cross multiply
    209.78x = 313.98 × 128.24
  4. Step 4: Simplify right side
    209.78x = 40,264.80
  5. Step 5: Solve for x
    x = 40,264.80/209.78
  6. Step 6: Final answer
    x = 191.94

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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.