Finding the Fourth Proportional to 1,085.66, 1,498.34 and 643.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,085.66 : 1,498.34 = 643.72 : x
2. Step 2: Convert to fraction form
   1,085.66/1,498.34 = 643.72/x
3. Step 3: Cross multiply
   1,085.66x = 1,498.34 × 643.72
4. Step 4: Simplify right side
   1,085.66x = 964,511.42
5. Step 5: Solve for x
   x = 964,511.42/1,085.66
6. Step 6: Final answer
   x = 888.41