Finding the Fourth Proportional to 91,381.72, 136,693.50 and 85,783

Step by Step Solution

1. Step 1: Write the proportion equation
   91,381.72 : 136,693.50 = 85,783 : x
2. Step 2: Convert to fraction form
   91,381.72/136,693.50 = 85,783/x
3. Step 3: Cross multiply
   91,381.72x = 136,693.50 × 85,783
4. Step 4: Simplify right side
   91,381.72x = 11,725,978,510.50
5. Step 5: Solve for x
   x = 11,725,978,510.50/91,381.72
6. Step 6: Final answer
   x = 128,318.65