Finding the Fourth Proportional to 1,428.86, 1,971.47 and 839.28

Step by Step Solution

1. Step 1: Write the proportion equation
   1,428.86 : 1,971.47 = 839.28 : x
2. Step 2: Convert to fraction form
   1,428.86/1,971.47 = 839.28/x
3. Step 3: Cross multiply
   1,428.86x = 1,971.47 × 839.28
4. Step 4: Simplify right side
   1,428.86x = 1,654,615.34
5. Step 5: Solve for x
   x = 1,654,615.34/1,428.86
6. Step 6: Final answer
   x = 1,158.00