Finding the Fourth Proportional to 1,428.76, 1,971.80 and 839.32

Step by Step Solution

1. Step 1: Write the proportion equation
   1,428.76 : 1,971.80 = 839.32 : x
2. Step 2: Convert to fraction form
   1,428.76/1,971.80 = 839.32/x
3. Step 3: Cross multiply
   1,428.76x = 1,971.80 × 839.32
4. Step 4: Simplify right side
   1,428.76x = 1,654,971.18
5. Step 5: Solve for x
   x = 1,654,971.18/1,428.76
6. Step 6: Final answer
   x = 1,158.33