Finding the Fourth Proportional to 1,105.68, 1,525.86 and 640.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,105.68 : 1,525.86 = 640.20 : x
2. Step 2: Convert to fraction form
   1,105.68/1,525.86 = 640.20/x
3. Step 3: Cross multiply
   1,105.68x = 1,525.86 × 640.20
4. Step 4: Simplify right side
   1,105.68x = 976,855.57
5. Step 5: Solve for x
   x = 976,855.57/1,105.68
6. Step 6: Final answer
   x = 883.49