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Finding the Fourth Proportional to 492.21, 678.38 and 393.80

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Solution

The fourth proportional to 492.21, 678.38 and 393.80 is: 542.74

Step by Step Solution

  1. Step 1: Write the proportion equation
    492.21 : 678.38 = 393.80 : x
  2. Step 2: Convert to fraction form
    492.21/678.38 = 393.80/x
  3. Step 3: Cross multiply
    492.21x = 678.38 × 393.80
  4. Step 4: Simplify right side
    492.21x = 267,140.68
  5. Step 5: Solve for x
    x = 267,140.68/492.21
  6. Step 6: Final answer
    x = 542.74

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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.