Finding the Fourth Proportional to 1,380.30, 1,904.81 and 790.89

Step by Step Solution

1. Step 1: Write the proportion equation
   1,380.30 : 1,904.81 = 790.89 : x
2. Step 2: Convert to fraction form
   1,380.30/1,904.81 = 790.89/x
3. Step 3: Cross multiply
   1,380.30x = 1,904.81 × 790.89
4. Step 4: Simplify right side
   1,380.30x = 1,506,495.18
5. Step 5: Solve for x
   x = 1,506,495.18/1,380.30
6. Step 6: Final answer
   x = 1,091.43