Finding the Fourth Proportional to 2,640.64, 3,961.56 and 1,407.40

Step by Step Solution

1. Step 1: Write the proportion equation
   2,640.64 : 3,961.56 = 1,407.40 : x
2. Step 2: Convert to fraction form
   2,640.64/3,961.56 = 1,407.40/x
3. Step 3: Cross multiply
   2,640.64x = 3,961.56 × 1,407.40
4. Step 4: Simplify right side
   2,640.64x = 5,575,499.54
5. Step 5: Solve for x
   x = 5,575,499.54/2,640.64
6. Step 6: Final answer
   x = 2,111.42