Finding the Fourth Proportional to 1,380.15, 1,904.75 and 790.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,380.15 : 1,904.75 = 790.57 : x
2. Step 2: Convert to fraction form
   1,380.15/1,904.75 = 790.57/x
3. Step 3: Cross multiply
   1,380.15x = 1,904.75 × 790.57
4. Step 4: Simplify right side
   1,380.15x = 1,505,839.60
5. Step 5: Solve for x
   x = 1,505,839.60/1,380.15
6. Step 6: Final answer
   x = 1,091.07