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Finding the Fourth Proportional to 5.21, 7.81 and 4

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Solution

The fourth proportional to 5.21, 7.81 and 4 is: 5.99

Step by Step Solution

  1. Step 1: Write the proportion equation
    5.21 : 7.81 = 4 : x
  2. Step 2: Convert to fraction form
    5.21/7.81 = 4/x
  3. Step 3: Cross multiply
    5.21x = 7.81 × 4
  4. Step 4: Simplify right side
    5.21x = 31.22
  5. Step 5: Solve for x
    x = 31.22/5.21
  6. Step 6: Final answer
    x = 5.99

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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.