Finding the Fourth Proportional to 1,428.69, 1,971.92 and 839.42

Step by Step Solution

1. Step 1: Write the proportion equation
   1,428.69 : 1,971.92 = 839.42 : x
2. Step 2: Convert to fraction form
   1,428.69/1,971.92 = 839.42/x
3. Step 3: Cross multiply
   1,428.69x = 1,971.92 × 839.42
4. Step 4: Simplify right side
   1,428.69x = 1,655,255.03
5. Step 5: Solve for x
   x = 1,655,255.03/1,428.69
6. Step 6: Final answer
   x = 1,158.58