Finding the Fourth Proportional to 1,085.69, 1,498.26 and 643.81

Step by Step Solution

1. Step 1: Write the proportion equation
   1,085.69 : 1,498.26 = 643.81 : x
2. Step 2: Convert to fraction form
   1,085.69/1,498.26 = 643.81/x
3. Step 3: Cross multiply
   1,085.69x = 1,498.26 × 643.81
4. Step 4: Simplify right side
   1,085.69x = 964,594.77
5. Step 5: Solve for x
   x = 964,594.77/1,085.69
6. Step 6: Final answer
   x = 888.46