Finding the Fourth Proportional to 139.12, 191.87 and 90.00

Step by Step Solution

1. Step 1: Write the proportion equation
   139.12 : 191.87 = 90.00 : x
2. Step 2: Convert to fraction form
   139.12/191.87 = 90.00/x
3. Step 3: Cross multiply
   139.12x = 191.87 × 90.00
4. Step 4: Simplify right side
   139.12x = 17,266.89
5. Step 5: Solve for x
   x = 17,266.89/139.12
6. Step 6: Final answer
   x = 124.12