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Finding the Fourth Proportional to 209.99, 315.12 and 128.58

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Solution

The fourth proportional to 209.99, 315.12 and 128.58 is: 192.96

Step by Step Solution

  1. Step 1: Write the proportion equation
    209.99 : 315.12 = 128.58 : x
  2. Step 2: Convert to fraction form
    209.99/315.12 = 128.58/x
  3. Step 3: Cross multiply
    209.99x = 315.12 × 128.58
  4. Step 4: Simplify right side
    209.99x = 40,518.13
  5. Step 5: Solve for x
    x = 40,518.13/209.99
  6. Step 6: Final answer
    x = 192.96

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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.