Finding the Fourth Proportional to 1,379.92, 1,904.34 and 790.40

Step by Step Solution

1. Step 1: Write the proportion equation
   1,379.92 : 1,904.34 = 790.40 : x
2. Step 2: Convert to fraction form
   1,379.92/1,904.34 = 790.40/x
3. Step 3: Cross multiply
   1,379.92x = 1,904.34 × 790.40
4. Step 4: Simplify right side
   1,379.92x = 1,505,190.34
5. Step 5: Solve for x
   x = 1,505,190.34/1,379.92
6. Step 6: Final answer
   x = 1,090.78