Finding the Fourth Proportional to 91,380.72, 136,692 and 85,782

Step by Step Solution

1. Step 1: Write the proportion equation
   91,380.72 : 136,692 = 85,782 : x
2. Step 2: Convert to fraction form
   91,380.72/136,692 = 85,782/x
3. Step 3: Cross multiply
   91,380.72x = 136,692 × 85,782
4. Step 4: Simplify right side
   91,380.72x = 11,725,713,144
5. Step 5: Solve for x
   x = 11,725,713,144/91,380.72
6. Step 6: Final answer
   x = 128,317.15