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Finding the Fourth Proportional to 261.21, 391.72 and 139.51

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Solution

The fourth proportional to 261.21, 391.72 and 139.51 is: 209.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    261.21 : 391.72 = 139.51 : x
  2. Step 2: Convert to fraction form
    261.21/391.72 = 139.51/x
  3. Step 3: Cross multiply
    261.21x = 391.72 × 139.51
  4. Step 4: Simplify right side
    261.21x = 54,648.86
  5. Step 5: Solve for x
    x = 54,648.86/261.21
  6. Step 6: Final answer
    x = 209.21

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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.