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Finding the Fourth Proportional to 20.99, 31.19 and 20.64

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Solution

The fourth proportional to 20.99, 31.19 and 20.64 is: 30.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.99 : 31.19 = 20.64 : x
  2. Step 2: Convert to fraction form
    20.99/31.19 = 20.64/x
  3. Step 3: Cross multiply
    20.99x = 31.19 × 20.64
  4. Step 4: Simplify right side
    20.99x = 643.66
  5. Step 5: Solve for x
    x = 643.66/20.99
  6. Step 6: Final answer
    x = 30.67

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.