Finding the Fourth Proportional to 1,640.39, 2,459.78 and 715.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,640.39 : 2,459.78 = 715.55 : x
2. Step 2: Convert to fraction form
   1,640.39/2,459.78 = 715.55/x
3. Step 3: Cross multiply
   1,640.39x = 2,459.78 × 715.55
4. Step 4: Simplify right side
   1,640.39x = 1,760,091.61
5. Step 5: Solve for x
   x = 1,760,091.61/1,640.39
6. Step 6: Final answer
   x = 1,072.97