Finding the Fourth Proportional to 1,081.35, 1,621.82 and 648

Step by Step Solution

1. Step 1: Write the proportion equation
   1,081.35 : 1,621.82 = 648 : x
2. Step 2: Convert to fraction form
   1,081.35/1,621.82 = 648/x
3. Step 3: Cross multiply
   1,081.35x = 1,621.82 × 648
4. Step 4: Simplify right side
   1,081.35x = 1,050,940.98
5. Step 5: Solve for x
   x = 1,050,940.98/1,081.35
6. Step 6: Final answer
   x = 971.88