Finding the Fourth Proportional to 1,428.06, 1,970.60 and 830.28

Step by Step Solution

1. Step 1: Write the proportion equation
   1,428.06 : 1,970.60 = 830.28 : x
2. Step 2: Convert to fraction form
   1,428.06/1,970.60 = 830.28/x
3. Step 3: Cross multiply
   1,428.06x = 1,970.60 × 830.28
4. Step 4: Simplify right side
   1,428.06x = 1,636,149.77
5. Step 5: Solve for x
   x = 1,636,149.77/1,428.06
6. Step 6: Final answer
   x = 1,145.72