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Finding the Fourth Proportional to 390.75, 537.40 and 311.13

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Solution

The fourth proportional to 390.75, 537.40 and 311.13 is: 427.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.75 : 537.40 = 311.13 : x
  2. Step 2: Convert to fraction form
    390.75/537.40 = 311.13/x
  3. Step 3: Cross multiply
    390.75x = 537.40 × 311.13
  4. Step 4: Simplify right side
    390.75x = 167,201.26
  5. Step 5: Solve for x
    x = 167,201.26/390.75
  6. Step 6: Final answer
    x = 427.90

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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.