Finding the Fourth Proportional to 139.20, 191.61 and 123

Step by Step Solution

1. Step 1: Write the proportion equation
   139.20 : 191.61 = 123 : x
2. Step 2: Convert to fraction form
   139.20/191.61 = 123/x
3. Step 3: Cross multiply
   139.20x = 191.61 × 123
4. Step 4: Simplify right side
   139.20x = 23,568.03
5. Step 5: Solve for x
   x = 23,568.03/139.20
6. Step 6: Final answer
   x = 169.31