Finding the Fourth Proportional to 1,085.94, 1,498.50 and 643.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,085.94 : 1,498.50 = 643.78 : x
2. Step 2: Convert to fraction form
   1,085.94/1,498.50 = 643.78/x
3. Step 3: Cross multiply
   1,085.94x = 1,498.50 × 643.78
4. Step 4: Simplify right side
   1,085.94x = 964,706.20
5. Step 5: Solve for x
   x = 964,706.20/1,085.94
6. Step 6: Final answer
   x = 888.36