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Finding the Fourth Proportional to 30.98, 42.65 and 28.80

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Solution

The fourth proportional to 30.98, 42.65 and 28.80 is: 39.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    30.98 : 42.65 = 28.80 : x
  2. Step 2: Convert to fraction form
    30.98/42.65 = 28.80/x
  3. Step 3: Cross multiply
    30.98x = 42.65 × 28.80
  4. Step 4: Simplify right side
    30.98x = 1,228.32
  5. Step 5: Solve for x
    x = 1,228.32/30.98
  6. Step 6: Final answer
    x = 39.65

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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.