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Finding the Fourth Proportional to 30.72, 42.17 and 28.74

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Solution

The fourth proportional to 30.72, 42.17 and 28.74 is: 39.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    30.72 : 42.17 = 28.74 : x
  2. Step 2: Convert to fraction form
    30.72/42.17 = 28.74/x
  3. Step 3: Cross multiply
    30.72x = 42.17 × 28.74
  4. Step 4: Simplify right side
    30.72x = 1,211.82
  5. Step 5: Solve for x
    x = 1,211.82/30.72
  6. Step 6: Final answer
    x = 39.45

Related Problems

Find fourth proportional to 15.36, 21.08 and 14.37
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Double scale
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Similar ratio
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1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.37) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.