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Finding the Fourth Proportional to 309.51, 428.09 and 287.91

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Solution

The fourth proportional to 309.51, 428.09 and 287.91 is: 398.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    309.51 : 428.09 = 287.91 : x
  2. Step 2: Convert to fraction form
    309.51/428.09 = 287.91/x
  3. Step 3: Cross multiply
    309.51x = 428.09 × 287.91
  4. Step 4: Simplify right side
    309.51x = 123,249.95
  5. Step 5: Solve for x
    x = 123,249.95/309.51
  6. Step 6: Final answer
    x = 398.21

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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.