Finding the Fourth Proportional to 139.76, 209.69 and 91.00

Step by Step Solution

1. Step 1: Write the proportion equation
   139.76 : 209.69 = 91.00 : x
2. Step 2: Convert to fraction form
   139.76/209.69 = 91.00/x
3. Step 3: Cross multiply
   139.76x = 209.69 × 91.00
4. Step 4: Simplify right side
   139.76x = 19,081.94
5. Step 5: Solve for x
   x = 19,081.94/139.76
6. Step 6: Final answer
   x = 136.53