Finding the Fourth Proportional to 91.08, 125.72 and 83.78

Step by Step Solution

1. Step 1: Write the proportion equation
   91.08 : 125.72 = 83.78 : x
2. Step 2: Convert to fraction form
   91.08/125.72 = 83.78/x
3. Step 3: Cross multiply
   91.08x = 125.72 × 83.78
4. Step 4: Simplify right side
   91.08x = 10,532.82
5. Step 5: Solve for x
   x = 10,532.82/91.08
6. Step 6: Final answer
   x = 115.64