Finding the Fourth Proportional to 1,420.40, 1,959.78 and 830.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,420.40 : 1,959.78 = 830.80 : x
2. Step 2: Convert to fraction form
   1,420.40/1,959.78 = 830.80/x
3. Step 3: Cross multiply
   1,420.40x = 1,959.78 × 830.80
4. Step 4: Simplify right side
   1,420.40x = 1,628,185.22
5. Step 5: Solve for x
   x = 1,628,185.22/1,420.40
6. Step 6: Final answer
   x = 1,146.29