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Finding the Fourth Proportional to 42.80, 64.21 and 13.91

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Solution

The fourth proportional to 42.80, 64.21 and 13.91 is: 20.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    42.80 : 64.21 = 13.91 : x
  2. Step 2: Convert to fraction form
    42.80/64.21 = 13.91/x
  3. Step 3: Cross multiply
    42.80x = 64.21 × 13.91
  4. Step 4: Simplify right side
    42.80x = 893.16
  5. Step 5: Solve for x
    x = 893.16/42.80
  6. Step 6: Final answer
    x = 20.87

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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.