Finding the Fourth Proportional to 2,085.77, 3,128.79 and 991.19

Step by Step Solution

1. Step 1: Write the proportion equation
   2,085.77 : 3,128.79 = 991.19 : x
2. Step 2: Convert to fraction form
   2,085.77/3,128.79 = 991.19/x
3. Step 3: Cross multiply
   2,085.77x = 3,128.79 × 991.19
4. Step 4: Simplify right side
   2,085.77x = 3,101,209.72
5. Step 5: Solve for x
   x = 3,101,209.72/2,085.77
6. Step 6: Final answer
   x = 1,486.85