Finding the Fourth Proportional to 1,085.90, 1,498.56 and 643.82

Step by Step Solution

1. Step 1: Write the proportion equation
   1,085.90 : 1,498.56 = 643.82 : x
2. Step 2: Convert to fraction form
   1,085.90/1,498.56 = 643.82/x
3. Step 3: Cross multiply
   1,085.90x = 1,498.56 × 643.82
4. Step 4: Simplify right side
   1,085.90x = 964,802.90
5. Step 5: Solve for x
   x = 964,802.90/1,085.90
6. Step 6: Final answer
   x = 888.48