Finding the Fourth Proportional to 139.28, 191.72 and 106.42

Step by Step Solution

1. Step 1: Write the proportion equation
   139.28 : 191.72 = 106.42 : x
2. Step 2: Convert to fraction form
   139.28/191.72 = 106.42/x
3. Step 3: Cross multiply
   139.28x = 191.72 × 106.42
4. Step 4: Simplify right side
   139.28x = 20,402.84
5. Step 5: Solve for x
   x = 20,402.84/139.28
6. Step 6: Final answer
   x = 146.49