Finding the Fourth Proportional to 1,381.86, 1,906.50 and 939

Step by Step Solution

1. Step 1: Write the proportion equation
   1,381.86 : 1,906.50 = 939 : x
2. Step 2: Convert to fraction form
   1,381.86/1,906.50 = 939/x
3. Step 3: Cross multiply
   1,381.86x = 1,906.50 × 939
4. Step 4: Simplify right side
   1,381.86x = 1,790,203.50
5. Step 5: Solve for x
   x = 1,790,203.50/1,381.86
6. Step 6: Final answer
   x = 1,295.50