Finding the Fourth Proportional to 1,085.95, 1,498.35 and 643.96

Step by Step Solution

1. Step 1: Write the proportion equation
   1,085.95 : 1,498.35 = 643.96 : x
2. Step 2: Convert to fraction form
   1,085.95/1,498.35 = 643.96/x
3. Step 3: Cross multiply
   1,085.95x = 1,498.35 × 643.96
4. Step 4: Simplify right side
   1,085.95x = 964,877.47
5. Step 5: Solve for x
   x = 964,877.47/1,085.95
6. Step 6: Final answer
   x = 888.51