Finding the Fourth Proportional to 1,085.60, 1,498.12 and 643.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,085.60 : 1,498.12 = 643.72 : x
2. Step 2: Convert to fraction form
   1,085.60/1,498.12 = 643.72/x
3. Step 3: Cross multiply
   1,085.60x = 1,498.12 × 643.72
4. Step 4: Simplify right side
   1,085.60x = 964,369.81
5. Step 5: Solve for x
   x = 964,369.81/1,085.60
6. Step 6: Final answer
   x = 888.33