Finding the Fourth Proportional to 1,420.30, 1,959.90 and 790.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,420.30 : 1,959.90 = 790.78 : x
2. Step 2: Convert to fraction form
   1,420.30/1,959.90 = 790.78/x
3. Step 3: Cross multiply
   1,420.30x = 1,959.90 × 790.78
4. Step 4: Simplify right side
   1,420.30x = 1,549,845.53
5. Step 5: Solve for x
   x = 1,549,845.53/1,420.30
6. Step 6: Final answer
   x = 1,091.21