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Finding the Fourth Proportional to 21.40, 31.91 and 20.74

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Solution

The fourth proportional to 21.40, 31.91 and 20.74 is: 30.93

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.40 : 31.91 = 20.74 : x
  2. Step 2: Convert to fraction form
    21.40/31.91 = 20.74/x
  3. Step 3: Cross multiply
    21.40x = 31.91 × 20.74
  4. Step 4: Simplify right side
    21.40x = 661.81
  5. Step 5: Solve for x
    x = 661.81/21.40
  6. Step 6: Final answer
    x = 30.93

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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.