Finding the Fourth Proportional to 1,105.55, 1,659 and 643.53

Step by Step Solution

1. Step 1: Write the proportion equation
   1,105.55 : 1,659 = 643.53 : x
2. Step 2: Convert to fraction form
   1,105.55/1,659 = 643.53/x
3. Step 3: Cross multiply
   1,105.55x = 1,659 × 643.53
4. Step 4: Simplify right side
   1,105.55x = 1,067,616.27
5. Step 5: Solve for x
   x = 1,067,616.27/1,105.55
6. Step 6: Final answer
   x = 965.69