Finding the Fourth Proportional to 1,311.60, 1,810.38 and 918.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,311.60 : 1,810.38 = 918.72 : x
2. Step 2: Convert to fraction form
   1,311.60/1,810.38 = 918.72/x
3. Step 3: Cross multiply
   1,311.60x = 1,810.38 × 918.72
4. Step 4: Simplify right side
   1,311.60x = 1,663,232.31
5. Step 5: Solve for x
   x = 1,663,232.31/1,311.60
6. Step 6: Final answer
   x = 1,268.09