Finding the Fourth Proportional to 91.40, 136.89 and 90.59

Step by Step Solution

1. Step 1: Write the proportion equation
   91.40 : 136.89 = 90.59 : x
2. Step 2: Convert to fraction form
   91.40/136.89 = 90.59/x
3. Step 3: Cross multiply
   91.40x = 136.89 × 90.59
4. Step 4: Simplify right side
   91.40x = 12,400.18
5. Step 5: Solve for x
   x = 12,400.18/91.40
6. Step 6: Final answer
   x = 135.68