Finding the Fourth Proportional to 1,085.76, 1,498.41 and 643.86

Step by Step Solution

1. Step 1: Write the proportion equation
   1,085.76 : 1,498.41 = 643.86 : x
2. Step 2: Convert to fraction form
   1,085.76/1,498.41 = 643.86/x
3. Step 3: Cross multiply
   1,085.76x = 1,498.41 × 643.86
4. Step 4: Simplify right side
   1,085.76x = 964,766.26
5. Step 5: Solve for x
   x = 964,766.26/1,085.76
6. Step 6: Final answer
   x = 888.56