Finding the Fourth Proportional to 1,558.10, 2,150.89 and 991.17

Step by Step Solution

1. Step 1: Write the proportion equation
   1,558.10 : 2,150.89 = 991.17 : x
2. Step 2: Convert to fraction form
   1,558.10/2,150.89 = 991.17/x
3. Step 3: Cross multiply
   1,558.10x = 2,150.89 × 991.17
4. Step 4: Simplify right side
   1,558.10x = 2,131,895.16
5. Step 5: Solve for x
   x = 2,131,895.16/1,558.10
6. Step 6: Final answer
   x = 1,368.26