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Finding the Fourth Proportional to 320.80, 480.78 and 138

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Solution

The fourth proportional to 320.80, 480.78 and 138 is: 206.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    320.80 : 480.78 = 138 : x
  2. Step 2: Convert to fraction form
    320.80/480.78 = 138/x
  3. Step 3: Cross multiply
    320.80x = 480.78 × 138
  4. Step 4: Simplify right side
    320.80x = 66,347.64
  5. Step 5: Solve for x
    x = 66,347.64/320.80
  6. Step 6: Final answer
    x = 206.82

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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.