Finding the Fourth Proportional to 91,379.72, 136,690.50 and 85,781

Step by Step Solution

1. Step 1: Write the proportion equation
   91,379.72 : 136,690.50 = 85,781 : x
2. Step 2: Convert to fraction form
   91,379.72/136,690.50 = 85,781/x
3. Step 3: Cross multiply
   91,379.72x = 136,690.50 × 85,781
4. Step 4: Simplify right side
   91,379.72x = 11,725,447,780.50
5. Step 5: Solve for x
   x = 11,725,447,780.50/91,379.72
6. Step 6: Final answer
   x = 128,315.65