Finding the Fourth Proportional to 1,385.80, 1,912.65 and 826.30

Step by Step Solution

1. Step 1: Write the proportion equation
   1,385.80 : 1,912.65 = 826.30 : x
2. Step 2: Convert to fraction form
   1,385.80/1,912.65 = 826.30/x
3. Step 3: Cross multiply
   1,385.80x = 1,912.65 × 826.30
4. Step 4: Simplify right side
   1,385.80x = 1,580,418.56
5. Step 5: Solve for x
   x = 1,580,418.56/1,385.80
6. Step 6: Final answer
   x = 1,140.44