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Finding the Fourth Proportional to 30.99, 42.77 and 21.78

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Solution

The fourth proportional to 30.99, 42.77 and 21.78 is: 30.06

Step by Step Solution

  1. Step 1: Write the proportion equation
    30.99 : 42.77 = 21.78 : x
  2. Step 2: Convert to fraction form
    30.99/42.77 = 21.78/x
  3. Step 3: Cross multiply
    30.99x = 42.77 × 21.78
  4. Step 4: Simplify right side
    30.99x = 931.53
  5. Step 5: Solve for x
    x = 931.53/30.99
  6. Step 6: Final answer
    x = 30.06

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.