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Finding the Fourth Proportional to 218.79, 328.15 and 81.80

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Solution

The fourth proportional to 218.79, 328.15 and 81.80 is: 122.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    218.79 : 328.15 = 81.80 : x
  2. Step 2: Convert to fraction form
    218.79/328.15 = 81.80/x
  3. Step 3: Cross multiply
    218.79x = 328.15 × 81.80
  4. Step 4: Simplify right side
    218.79x = 26,842.26
  5. Step 5: Solve for x
    x = 26,842.26/218.79
  6. Step 6: Final answer
    x = 122.69

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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.