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Finding the Fourth Proportional to 42.98, 64.40 and 20.15

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Solution

The fourth proportional to 42.98, 64.40 and 20.15 is: 30.19

Step by Step Solution

  1. Step 1: Write the proportion equation
    42.98 : 64.40 = 20.15 : x
  2. Step 2: Convert to fraction form
    42.98/64.40 = 20.15/x
  3. Step 3: Cross multiply
    42.98x = 64.40 × 20.15
  4. Step 4: Simplify right side
    42.98x = 1,297.24
  5. Step 5: Solve for x
    x = 1,297.24/42.98
  6. Step 6: Final answer
    x = 30.19

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.