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Finding the Fourth Proportional to 30.78, 42.81 and 30.12

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Solution

The fourth proportional to 30.78, 42.81 and 30.12 is: 41.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    30.78 : 42.81 = 30.12 : x
  2. Step 2: Convert to fraction form
    30.78/42.81 = 30.12/x
  3. Step 3: Cross multiply
    30.78x = 42.81 × 30.12
  4. Step 4: Simplify right side
    30.78x = 1,289.44
  5. Step 5: Solve for x
    x = 1,289.44/30.78
  6. Step 6: Final answer
    x = 41.89

Related Problems

Find fourth proportional to 15.39, 21.41 and 15.06
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Double scale
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1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.39) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.