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Finding the Fourth Proportional to 21, 31.68 and 20.79

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Solution

The fourth proportional to 21, 31.68 and 20.79 is: 31.36

Step by Step Solution

  1. Step 1: Write the proportion equation
    21 : 31.68 = 20.79 : x
  2. Step 2: Convert to fraction form
    21/31.68 = 20.79/x
  3. Step 3: Cross multiply
    21x = 31.68 × 20.79
  4. Step 4: Simplify right side
    21x = 658.63
  5. Step 5: Solve for x
    x = 658.63/21
  6. Step 6: Final answer
    x = 31.36

Related Problems

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Double scale
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Similar ratio
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1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.