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Finding the Fourth Proportional to 405.40, 607.20 and 212.80

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Solution

The fourth proportional to 405.40, 607.20 and 212.80 is: 318.73

Step by Step Solution

  1. Step 1: Write the proportion equation
    405.40 : 607.20 = 212.80 : x
  2. Step 2: Convert to fraction form
    405.40/607.20 = 212.80/x
  3. Step 3: Cross multiply
    405.40x = 607.20 × 212.80
  4. Step 4: Simplify right side
    405.40x = 129,212.16
  5. Step 5: Solve for x
    x = 129,212.16/405.40
  6. Step 6: Final answer
    x = 318.73

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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.