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Finding the Fourth Proportional to 139.56, 209.28 and 78.64

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Solution

The fourth proportional to 139.56, 209.28 and 78.64 is: 117.93

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.56 : 209.28 = 78.64 : x
  2. Step 2: Convert to fraction form
    139.56/209.28 = 78.64/x
  3. Step 3: Cross multiply
    139.56x = 209.28 × 78.64
  4. Step 4: Simplify right side
    139.56x = 16,457.55
  5. Step 5: Solve for x
    x = 16,457.55/139.56
  6. Step 6: Final answer
    x = 117.93

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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.