Finding the Fourth Proportional to 1,420.15, 1,959.80 and 790.64

Step by Step Solution

1. Step 1: Write the proportion equation
   1,420.15 : 1,959.80 = 790.64 : x
2. Step 2: Convert to fraction form
   1,420.15/1,959.80 = 790.64/x
3. Step 3: Cross multiply
   1,420.15x = 1,959.80 × 790.64
4. Step 4: Simplify right side
   1,420.15x = 1,549,500.89
5. Step 5: Solve for x
   x = 1,549,500.89/1,420.15
6. Step 6: Final answer
   x = 1,091.08