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Finding the Fourth Proportional to 30.40, 42.02 and 28.72

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Solution

The fourth proportional to 30.40, 42.02 and 28.72 is: 39.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    30.40 : 42.02 = 28.72 : x
  2. Step 2: Convert to fraction form
    30.40/42.02 = 28.72/x
  3. Step 3: Cross multiply
    30.40x = 42.02 × 28.72
  4. Step 4: Simplify right side
    30.40x = 1,206.81
  5. Step 5: Solve for x
    x = 1,206.81/30.40
  6. Step 6: Final answer
    x = 39.70

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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.