Finding the Fourth Proportional to 1,096.96, 1,643.52 and 640

Step by Step Solution

1. Step 1: Write the proportion equation
   1,096.96 : 1,643.52 = 640 : x
2. Step 2: Convert to fraction form
   1,096.96/1,643.52 = 640/x
3. Step 3: Cross multiply
   1,096.96x = 1,643.52 × 640
4. Step 4: Simplify right side
   1,096.96x = 1,051,852.80
5. Step 5: Solve for x
   x = 1,051,852.80/1,096.96
6. Step 6: Final answer
   x = 958.88