Finding the Fourth Proportional to 2,618.40, 3,928.56 and 1,320

Step by Step Solution

1. Step 1: Write the proportion equation
   2,618.40 : 3,928.56 = 1,320 : x
2. Step 2: Convert to fraction form
   2,618.40/3,928.56 = 1,320/x
3. Step 3: Cross multiply
   2,618.40x = 3,928.56 × 1,320
4. Step 4: Simplify right side
   2,618.40x = 5,185,699.20
5. Step 5: Solve for x
   x = 5,185,699.20/2,618.40
6. Step 6: Final answer
   x = 1,980.48