Finding the Fourth Proportional to 1,279.37, 1,917.34 and 661.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,279.37 : 1,917.34 = 661.78 : x
2. Step 2: Convert to fraction form
   1,279.37/1,917.34 = 661.78/x
3. Step 3: Cross multiply
   1,279.37x = 1,917.34 × 661.78
4. Step 4: Simplify right side
   1,279.37x = 1,268,858.01
5. Step 5: Solve for x
   x = 1,268,858.01/1,279.37
6. Step 6: Final answer
   x = 991.78