Finding the Fourth Proportional to 2,128.10, 3,192.60 and 647.20

Step by Step Solution

1. Step 1: Write the proportion equation
   2,128.10 : 3,192.60 = 647.20 : x
2. Step 2: Convert to fraction form
   2,128.10/3,192.60 = 647.20/x
3. Step 3: Cross multiply
   2,128.10x = 3,192.60 × 647.20
4. Step 4: Simplify right side
   2,128.10x = 2,066,250.72
5. Step 5: Solve for x
   x = 2,066,250.72/2,128.10
6. Step 6: Final answer
   x = 970.94