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Finding the Fourth Proportional to 31.18, 42.98 and 20.80

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Solution

The fourth proportional to 31.18, 42.98 and 20.80 is: 28.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.18 : 42.98 = 20.80 : x
  2. Step 2: Convert to fraction form
    31.18/42.98 = 20.80/x
  3. Step 3: Cross multiply
    31.18x = 42.98 × 20.80
  4. Step 4: Simplify right side
    31.18x = 893.98
  5. Step 5: Solve for x
    x = 893.98/31.18
  6. Step 6: Final answer
    x = 28.67

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.