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Finding the Fourth Proportional to 261.76, 391.60 and 221.28

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Solution

The fourth proportional to 261.76, 391.60 and 221.28 is: 331.04

Step by Step Solution

  1. Step 1: Write the proportion equation
    261.76 : 391.60 = 221.28 : x
  2. Step 2: Convert to fraction form
    261.76/391.60 = 221.28/x
  3. Step 3: Cross multiply
    261.76x = 391.60 × 221.28
  4. Step 4: Simplify right side
    261.76x = 86,653.25
  5. Step 5: Solve for x
    x = 86,653.25/261.76
  6. Step 6: Final answer
    x = 331.04

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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.