Finding the Fourth Proportional to 1,090.86, 1,505.10 and 618.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,090.86 : 1,505.10 = 618.78 : x
2. Step 2: Convert to fraction form
   1,090.86/1,505.10 = 618.78/x
3. Step 3: Cross multiply
   1,090.86x = 1,505.10 × 618.78
4. Step 4: Simplify right side
   1,090.86x = 931,325.78
5. Step 5: Solve for x
   x = 931,325.78/1,090.86
6. Step 6: Final answer
   x = 853.75