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Finding the Fourth Proportional to 211.20, 316.80 and 120

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Solution

The fourth proportional to 211.20, 316.80 and 120 is: 180

Step by Step Solution

  1. Step 1: Write the proportion equation
    211.20 : 316.80 = 120 : x
  2. Step 2: Convert to fraction form
    211.20/316.80 = 120/x
  3. Step 3: Cross multiply
    211.20x = 316.80 × 120
  4. Step 4: Simplify right side
    211.20x = 38,016
  5. Step 5: Solve for x
    x = 38,016/211.20
  6. Step 6: Final answer
    x = 180

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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.