Finding the Fourth Proportional to 1,388.10, 2,084.18 and 842.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.10 : 2,084.18 = 842.57 : x
2. Step 2: Convert to fraction form
   1,388.10/2,084.18 = 842.57/x
3. Step 3: Cross multiply
   1,388.10x = 2,084.18 × 842.57
4. Step 4: Simplify right side
   1,388.10x = 1,756,067.54
5. Step 5: Solve for x
   x = 1,756,067.54/1,388.10
6. Step 6: Final answer
   x = 1,265.09