Finding the Fourth Proportional to 2,085.25, 3,128.30 and 931

Step by Step Solution

1. Step 1: Write the proportion equation
   2,085.25 : 3,128.30 = 931 : x
2. Step 2: Convert to fraction form
   2,085.25/3,128.30 = 931/x
3. Step 3: Cross multiply
   2,085.25x = 3,128.30 × 931
4. Step 4: Simplify right side
   2,085.25x = 2,912,447.30
5. Step 5: Solve for x
   x = 2,912,447.30/2,085.25
6. Step 6: Final answer
   x = 1,396.69