Finding the Fourth Proportional to 1,136.90, 1,568.72 and 639.36

Step by Step Solution

1. Step 1: Write the proportion equation
   1,136.90 : 1,568.72 = 639.36 : x
2. Step 2: Convert to fraction form
   1,136.90/1,568.72 = 639.36/x
3. Step 3: Cross multiply
   1,136.90x = 1,568.72 × 639.36
4. Step 4: Simplify right side
   1,136.90x = 1,002,968.20
5. Step 5: Solve for x
   x = 1,002,968.20/1,136.90
6. Step 6: Final answer
   x = 882.20