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Finding the Fourth Proportional to 21, 31.49 and 20.51

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Solution

The fourth proportional to 21, 31.49 and 20.51 is: 30.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    21 : 31.49 = 20.51 : x
  2. Step 2: Convert to fraction form
    21/31.49 = 20.51/x
  3. Step 3: Cross multiply
    21x = 31.49 × 20.51
  4. Step 4: Simplify right side
    21x = 645.86
  5. Step 5: Solve for x
    x = 645.86/21
  6. Step 6: Final answer
    x = 30.76

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 (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.