Finding the Fourth Proportional to 1,191.31, 1,787.27 and 643.49

Step by Step Solution

1. Step 1: Write the proportion equation
   1,191.31 : 1,787.27 = 643.49 : x
2. Step 2: Convert to fraction form
   1,191.31/1,787.27 = 643.49/x
3. Step 3: Cross multiply
   1,191.31x = 1,787.27 × 643.49
4. Step 4: Simplify right side
   1,191.31x = 1,150,094.97
5. Step 5: Solve for x
   x = 1,150,094.97/1,191.31
6. Step 6: Final answer
   x = 965.41