Finding the Fourth Proportional to 91,719.30, 128,640.30 and 91,719.30

Step by Step Solution

1. Step 1: Write the proportion equation
   91,719.30 : 128,640.30 = 91,719.30 : x
2. Step 2: Convert to fraction form
   91,719.30/128,640.30 = 91,719.30/x
3. Step 3: Cross multiply
   91,719.30x = 128,640.30 × 91,719.30
4. Step 4: Simplify right side
   91,719.30x = 11,798,798,267.79
5. Step 5: Solve for x
   x = 11,798,798,267.79/91,719.30
6. Step 6: Final answer
   x = 128,640.30