Finding the Fourth Proportional to 1,085.90, 1,500.99 and 999.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,085.90 : 1,500.99 = 999.78 : x
2. Step 2: Convert to fraction form
   1,085.90/1,500.99 = 999.78/x
3. Step 3: Cross multiply
   1,085.90x = 1,500.99 × 999.78
4. Step 4: Simplify right side
   1,085.90x = 1,500,659.78
5. Step 5: Solve for x
   x = 1,500,659.78/1,085.90
6. Step 6: Final answer
   x = 1,381.96