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Finding the Fourth Proportional to 21.38, 31.86 and 20

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Solution

The fourth proportional to 21.38, 31.86 and 20 is: 29.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.38 : 31.86 = 20 : x
  2. Step 2: Convert to fraction form
    21.38/31.86 = 20/x
  3. Step 3: Cross multiply
    21.38x = 31.86 × 20
  4. Step 4: Simplify right side
    21.38x = 637.20
  5. Step 5: Solve for x
    x = 637.20/21.38
  6. Step 6: Final answer
    x = 29.80

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1.5x scale

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.