Finding the Fourth Proportional to 1,355.78, 1,870.94 and 890

Step by Step Solution

1. Step 1: Write the proportion equation
   1,355.78 : 1,870.94 = 890 : x
2. Step 2: Convert to fraction form
   1,355.78/1,870.94 = 890/x
3. Step 3: Cross multiply
   1,355.78x = 1,870.94 × 890
4. Step 4: Simplify right side
   1,355.78x = 1,665,136.60
5. Step 5: Solve for x
   x = 1,665,136.60/1,355.78
6. Step 6: Final answer
   x = 1,228.18