Finding the Third Proportional to 90.15 and 138.19

Step by Step Solution

1. Step 1: Write the proportion equation
   90.15 : 138.19 = 138.19 : x
2. Step 2: Convert to fraction form
   90.15/138.19 = 138.19/x
3. Step 3: Cross multiply
   90.15x = 138.19 × 138.19
4. Step 4: Simplify right side
   90.15x = 19,096.59
5. Step 5: Solve for x
   x = 19,096.59/90.15
6. Step 6: Final answer
   x = 211.83