Finding the Fourth Proportional to 3,398.79, 5,091.61 and 1,989.80

Step by Step Solution

1. Step 1: Write the proportion equation
   3,398.79 : 5,091.61 = 1,989.80 : x
2. Step 2: Convert to fraction form
   3,398.79/5,091.61 = 1,989.80/x
3. Step 3: Cross multiply
   3,398.79x = 5,091.61 × 1,989.80
4. Step 4: Simplify right side
   3,398.79x = 10,131,255.15
5. Step 5: Solve for x
   x = 10,131,255.15/3,398.79
6. Step 6: Final answer
   x = 2,980.84