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Finding the Fourth Proportional to 221.65, 305.91 and 128.42

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Solution

The fourth proportional to 221.65, 305.91 and 128.42 is: 177.23

Step by Step Solution

  1. Step 1: Write the proportion equation
    221.65 : 305.91 = 128.42 : x
  2. Step 2: Convert to fraction form
    221.65/305.91 = 128.42/x
  3. Step 3: Cross multiply
    221.65x = 305.91 × 128.42
  4. Step 4: Simplify right side
    221.65x = 39,284.58
  5. Step 5: Solve for x
    x = 39,284.58/221.65
  6. Step 6: Final answer
    x = 177.23

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.