Finding the Fourth Proportional to 1,428.72, 1,971.77 and 839.24

Step by Step Solution

1. Step 1: Write the proportion equation
   1,428.72 : 1,971.77 = 839.24 : x
2. Step 2: Convert to fraction form
   1,428.72/1,971.77 = 839.24/x
3. Step 3: Cross multiply
   1,428.72x = 1,971.77 × 839.24
4. Step 4: Simplify right side
   1,428.72x = 1,654,788.25
5. Step 5: Solve for x
   x = 1,654,788.25/1,428.72
6. Step 6: Final answer
   x = 1,158.23