Finding the Fourth Proportional to 2,086.80, 3,131.10 and 990.60

Step by Step Solution

1. Step 1: Write the proportion equation
   2,086.80 : 3,131.10 = 990.60 : x
2. Step 2: Convert to fraction form
   2,086.80/3,131.10 = 990.60/x
3. Step 3: Cross multiply
   2,086.80x = 3,131.10 × 990.60
4. Step 4: Simplify right side
   2,086.80x = 3,101,667.66
5. Step 5: Solve for x
   x = 3,101,667.66/2,086.80
6. Step 6: Final answer
   x = 1,486.33