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Finding the Fourth Proportional to 30.83, 42.56 and 21

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Solution

The fourth proportional to 30.83, 42.56 and 21 is: 28.99

Step by Step Solution

  1. Step 1: Write the proportion equation
    30.83 : 42.56 = 21 : x
  2. Step 2: Convert to fraction form
    30.83/42.56 = 21/x
  3. Step 3: Cross multiply
    30.83x = 42.56 × 21
  4. Step 4: Simplify right side
    30.83x = 893.76
  5. Step 5: Solve for x
    x = 893.76/30.83
  6. Step 6: Final answer
    x = 28.99

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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.