Finding the Fourth Proportional to 2,131.78, 2,940.91 and 1,247.20

Step by Step Solution

1. Step 1: Write the proportion equation
   2,131.78 : 2,940.91 = 1,247.20 : x
2. Step 2: Convert to fraction form
   2,131.78/2,940.91 = 1,247.20/x
3. Step 3: Cross multiply
   2,131.78x = 2,940.91 × 1,247.20
4. Step 4: Simplify right side
   2,131.78x = 3,667,902.95
5. Step 5: Solve for x
   x = 3,667,902.95/2,131.78
6. Step 6: Final answer
   x = 1,720.58