Finding the Fourth Proportional to 1,165.78, 1,608.72 and 641.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,165.78 : 1,608.72 = 641.80 : x
2. Step 2: Convert to fraction form
   1,165.78/1,608.72 = 641.80/x
3. Step 3: Cross multiply
   1,165.78x = 1,608.72 × 641.80
4. Step 4: Simplify right side
   1,165.78x = 1,032,476.50
5. Step 5: Solve for x
   x = 1,032,476.50/1,165.78
6. Step 6: Final answer
   x = 885.65