Finding the Fourth Proportional to 1,172.97, 1,618.72 and 641.86

Step by Step Solution

1. Step 1: Write the proportion equation
   1,172.97 : 1,618.72 = 641.86 : x
2. Step 2: Convert to fraction form
   1,172.97/1,618.72 = 641.86/x
3. Step 3: Cross multiply
   1,172.97x = 1,618.72 × 641.86
4. Step 4: Simplify right side
   1,172.97x = 1,038,995.50
5. Step 5: Solve for x
   x = 1,038,995.50/1,172.97
6. Step 6: Final answer
   x = 885.78