Finding the Fourth Proportional to 1,291.72, 1,936.86 and 641.56

Step by Step Solution

1. Step 1: Write the proportion equation
   1,291.72 : 1,936.86 = 641.56 : x
2. Step 2: Convert to fraction form
   1,291.72/1,936.86 = 641.56/x
3. Step 3: Cross multiply
   1,291.72x = 1,936.86 × 641.56
4. Step 4: Simplify right side
   1,291.72x = 1,242,611.90
5. Step 5: Solve for x
   x = 1,242,611.90/1,291.72
6. Step 6: Final answer
   x = 961.98