Finding the Fourth Proportional to 1,428.80, 1,971.77 and 869.29

Step by Step Solution

1. Step 1: Write the proportion equation
   1,428.80 : 1,971.77 = 869.29 : x
2. Step 2: Convert to fraction form
   1,428.80/1,971.77 = 869.29/x
3. Step 3: Cross multiply
   1,428.80x = 1,971.77 × 869.29
4. Step 4: Simplify right side
   1,428.80x = 1,714,035.60
5. Step 5: Solve for x
   x = 1,714,035.60/1,428.80
6. Step 6: Final answer
   x = 1,199.64