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Finding the Fourth Proportional to 30.74, 42.40 and 21.53

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Solution

The fourth proportional to 30.74, 42.40 and 21.53 is: 29.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    30.74 : 42.40 = 21.53 : x
  2. Step 2: Convert to fraction form
    30.74/42.40 = 21.53/x
  3. Step 3: Cross multiply
    30.74x = 42.40 × 21.53
  4. Step 4: Simplify right side
    30.74x = 912.55
  5. Step 5: Solve for x
    x = 912.55/30.74
  6. Step 6: Final answer
    x = 29.69

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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.