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Finding the Fourth Proportional to 391.75, 538.78 and 312.13

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Solution

The fourth proportional to 391.75, 538.78 and 312.13 is: 429.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    391.75 : 538.78 = 312.13 : x
  2. Step 2: Convert to fraction form
    391.75/538.78 = 312.13/x
  3. Step 3: Cross multiply
    391.75x = 538.78 × 312.13
  4. Step 4: Simplify right side
    391.75x = 168,169.40
  5. Step 5: Solve for x
    x = 168,169.40/391.75
  6. Step 6: Final answer
    x = 429.28

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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.