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Finding the Fourth Proportional to 386.40, 579.60 and 213.60

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Solution

The fourth proportional to 386.40, 579.60 and 213.60 is: 320.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    386.40 : 579.60 = 213.60 : x
  2. Step 2: Convert to fraction form
    386.40/579.60 = 213.60/x
  3. Step 3: Cross multiply
    386.40x = 579.60 × 213.60
  4. Step 4: Simplify right side
    386.40x = 123,802.56
  5. Step 5: Solve for x
    x = 123,802.56/386.40
  6. Step 6: Final answer
    x = 320.40

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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.