Finding the Fourth Proportional to 1,390.37, 1,918.91 and 800.90

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.37 : 1,918.91 = 800.90 : x
2. Step 2: Convert to fraction form
   1,390.37/1,918.91 = 800.90/x
3. Step 3: Cross multiply
   1,390.37x = 1,918.91 × 800.90
4. Step 4: Simplify right side
   1,390.37x = 1,536,841.42
5. Step 5: Solve for x
   x = 1,536,841.42/1,390.37
6. Step 6: Final answer
   x = 1,105.35