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Finding the Fourth Proportional to 112.80, 169.20 and 85.68

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Solution

The fourth proportional to 112.80, 169.20 and 85.68 is: 128.52

Step by Step Solution

  1. Step 1: Write the proportion equation
    112.80 : 169.20 = 85.68 : x
  2. Step 2: Convert to fraction form
    112.80/169.20 = 85.68/x
  3. Step 3: Cross multiply
    112.80x = 169.20 × 85.68
  4. Step 4: Simplify right side
    112.80x = 14,497.06
  5. Step 5: Solve for x
    x = 14,497.06/112.80
  6. Step 6: Final answer
    x = 128.52

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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.