Finding the Fourth Proportional to 99.78, 149.33 and 91.35

Step by Step Solution

1. Step 1: Write the proportion equation
   99.78 : 149.33 = 91.35 : x
2. Step 2: Convert to fraction form
   99.78/149.33 = 91.35/x
3. Step 3: Cross multiply
   99.78x = 149.33 × 91.35
4. Step 4: Simplify right side
   99.78x = 13,641.82
5. Step 5: Solve for x
   x = 13,641.82/99.78
6. Step 6: Final answer
   x = 136.72