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Finding the Fourth Proportional to 138.24, 190.80 and 86.40

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Solution

The fourth proportional to 138.24, 190.80 and 86.40 is: 119.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.24 : 190.80 = 86.40 : x
  2. Step 2: Convert to fraction form
    138.24/190.80 = 86.40/x
  3. Step 3: Cross multiply
    138.24x = 190.80 × 86.40
  4. Step 4: Simplify right side
    138.24x = 16,485.12
  5. Step 5: Solve for x
    x = 16,485.12/138.24
  6. Step 6: Final answer
    x = 119.25

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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.