Finding the Fourth Proportional to 1,421.20, 1,961.37 and 791.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,421.20 : 1,961.37 = 791.78 : x
2. Step 2: Convert to fraction form
   1,421.20/1,961.37 = 791.78/x
3. Step 3: Cross multiply
   1,421.20x = 1,961.37 × 791.78
4. Step 4: Simplify right side
   1,421.20x = 1,552,973.54
5. Step 5: Solve for x
   x = 1,552,973.54/1,421.20
6. Step 6: Final answer
   x = 1,092.72