Finding the Fourth Proportional to 1,111.40, 1,665.10 and 648.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,111.40 : 1,665.10 = 648.80 : x
2. Step 2: Convert to fraction form
   1,111.40/1,665.10 = 648.80/x
3. Step 3: Cross multiply
   1,111.40x = 1,665.10 × 648.80
4. Step 4: Simplify right side
   1,111.40x = 1,080,316.88
5. Step 5: Solve for x
   x = 1,080,316.88/1,111.40
6. Step 6: Final answer
   x = 972.03