Finding the Fourth Proportional to 2,087.16, 3,131.28 and 991.50

Step by Step Solution

1. Step 1: Write the proportion equation
   2,087.16 : 3,131.28 = 991.50 : x
2. Step 2: Convert to fraction form
   2,087.16/3,131.28 = 991.50/x
3. Step 3: Cross multiply
   2,087.16x = 3,131.28 × 991.50
4. Step 4: Simplify right side
   2,087.16x = 3,104,664.12
5. Step 5: Solve for x
   x = 3,104,664.12/2,087.16
6. Step 6: Final answer
   x = 1,487.51