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Finding the Fourth Proportional to 21.47, 29.77 and 20.78

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Solution

The fourth proportional to 21.47, 29.77 and 20.78 is: 28.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.47 : 29.77 = 20.78 : x
  2. Step 2: Convert to fraction form
    21.47/29.77 = 20.78/x
  3. Step 3: Cross multiply
    21.47x = 29.77 × 20.78
  4. Step 4: Simplify right side
    21.47x = 618.62
  5. Step 5: Solve for x
    x = 618.62/21.47
  6. Step 6: Final answer
    x = 28.82

Related Problems

Find fourth proportional to 10.73, 14.89 and 10.39
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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 (1.39) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.