Finding the Fourth Proportional to 1,105.15, 1,657.18 and 643.09

Step by Step Solution

1. Step 1: Write the proportion equation
   1,105.15 : 1,657.18 = 643.09 : x
2. Step 2: Convert to fraction form
   1,105.15/1,657.18 = 643.09/x
3. Step 3: Cross multiply
   1,105.15x = 1,657.18 × 643.09
4. Step 4: Simplify right side
   1,105.15x = 1,065,715.89
5. Step 5: Solve for x
   x = 1,065,715.89/1,105.15
6. Step 6: Final answer
   x = 964.32