Finding the Fourth Proportional to 1,085.88, 1,498.71 and 643.94

Step by Step Solution

1. Step 1: Write the proportion equation
   1,085.88 : 1,498.71 = 643.94 : x
2. Step 2: Convert to fraction form
   1,085.88/1,498.71 = 643.94/x
3. Step 3: Cross multiply
   1,085.88x = 1,498.71 × 643.94
4. Step 4: Simplify right side
   1,085.88x = 965,079.32
5. Step 5: Solve for x
   x = 965,079.32/1,085.88
6. Step 6: Final answer
   x = 888.75