Finding the Third Proportional to 90.21 and 128.18

Step by Step Solution

1. Step 1: Write the proportion equation
   90.21 : 128.18 = 128.18 : x
2. Step 2: Convert to fraction form
   90.21/128.18 = 128.18/x
3. Step 3: Cross multiply
   90.21x = 128.18 × 128.18
4. Step 4: Simplify right side
   90.21x = 16,430.03
5. Step 5: Solve for x
   x = 16,430.03/90.21
6. Step 6: Final answer
   x = 182.13