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Finding the Fourth Proportional to 78.21, 117.34 and 42.13

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Solution

The fourth proportional to 78.21, 117.34 and 42.13 is: 63.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.21 : 117.34 = 42.13 : x
  2. Step 2: Convert to fraction form
    78.21/117.34 = 42.13/x
  3. Step 3: Cross multiply
    78.21x = 117.34 × 42.13
  4. Step 4: Simplify right side
    78.21x = 4,942.95
  5. Step 5: Solve for x
    x = 4,942.95/78.21
  6. Step 6: Final answer
    x = 63.21

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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.