Finding the Fourth Proportional to 1,428.64, 1,971.89 and 869.48

Step by Step Solution

1. Step 1: Write the proportion equation
   1,428.64 : 1,971.89 = 869.48 : x
2. Step 2: Convert to fraction form
   1,428.64/1,971.89 = 869.48/x
3. Step 3: Cross multiply
   1,428.64x = 1,971.89 × 869.48
4. Step 4: Simplify right side
   1,428.64x = 1,714,531.35
5. Step 5: Solve for x
   x = 1,714,531.35/1,428.64
6. Step 6: Final answer
   x = 1,200.12