Finding the Fourth Proportional to 1,428.81, 1,971.89 and 869.15

Step by Step Solution

1. Step 1: Write the proportion equation
   1,428.81 : 1,971.89 = 869.15 : x
2. Step 2: Convert to fraction form
   1,428.81/1,971.89 = 869.15/x
3. Step 3: Cross multiply
   1,428.81x = 1,971.89 × 869.15
4. Step 4: Simplify right side
   1,428.81x = 1,713,853.99
5. Step 5: Solve for x
   x = 1,713,853.99/1,428.81
6. Step 6: Final answer
   x = 1,199.50