Finding the Fourth Proportional to 1,385.78, 1,912.15 and 826.05

Step by Step Solution

1. Step 1: Write the proportion equation
   1,385.78 : 1,912.15 = 826.05 : x
2. Step 2: Convert to fraction form
   1,385.78/1,912.15 = 826.05/x
3. Step 3: Cross multiply
   1,385.78x = 1,912.15 × 826.05
4. Step 4: Simplify right side
   1,385.78x = 1,579,531.51
5. Step 5: Solve for x
   x = 1,579,531.51/1,385.78
6. Step 6: Final answer
   x = 1,139.81