Finding the Fourth Proportional to 1,390.28, 1,918.50 and 800.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.28 : 1,918.50 = 800.72 : x
2. Step 2: Convert to fraction form
   1,390.28/1,918.50 = 800.72/x
3. Step 3: Cross multiply
   1,390.28x = 1,918.50 × 800.72
4. Step 4: Simplify right side
   1,390.28x = 1,536,181.32
5. Step 5: Solve for x
   x = 1,536,181.32/1,390.28
6. Step 6: Final answer
   x = 1,104.94