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Finding the Fourth Proportional to 139.64, 192.72 and 87.20

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Solution

The fourth proportional to 139.64, 192.72 and 87.20 is: 120.35

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.64 : 192.72 = 87.20 : x
  2. Step 2: Convert to fraction form
    139.64/192.72 = 87.20/x
  3. Step 3: Cross multiply
    139.64x = 192.72 × 87.20
  4. Step 4: Simplify right side
    139.64x = 16,805.18
  5. Step 5: Solve for x
    x = 16,805.18/139.64
  6. Step 6: Final answer
    x = 120.35

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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.