Finding the Fourth Proportional to 1,428.74, 1,971.60 and 839.34

Step by Step Solution

1. Step 1: Write the proportion equation
   1,428.74 : 1,971.60 = 839.34 : x
2. Step 2: Convert to fraction form
   1,428.74/1,971.60 = 839.34/x
3. Step 3: Cross multiply
   1,428.74x = 1,971.60 × 839.34
4. Step 4: Simplify right side
   1,428.74x = 1,654,842.74
5. Step 5: Solve for x
   x = 1,654,842.74/1,428.74
6. Step 6: Final answer
   x = 1,158.25