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Finding the Fourth Proportional to 212.40, 318.60 and 115.20

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Solution

The fourth proportional to 212.40, 318.60 and 115.20 is: 172.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    212.40 : 318.60 = 115.20 : x
  2. Step 2: Convert to fraction form
    212.40/318.60 = 115.20/x
  3. Step 3: Cross multiply
    212.40x = 318.60 × 115.20
  4. Step 4: Simplify right side
    212.40x = 36,702.72
  5. Step 5: Solve for x
    x = 36,702.72/212.40
  6. Step 6: Final answer
    x = 172.80

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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.