Finding the Fourth Proportional to 2,652.36, 3,978.72 and 921.12

Step by Step Solution

1. Step 1: Write the proportion equation
   2,652.36 : 3,978.72 = 921.12 : x
2. Step 2: Convert to fraction form
   2,652.36/3,978.72 = 921.12/x
3. Step 3: Cross multiply
   2,652.36x = 3,978.72 × 921.12
4. Step 4: Simplify right side
   2,652.36x = 3,664,878.57
5. Step 5: Solve for x
   x = 3,664,878.57/2,652.36
6. Step 6: Final answer
   x = 1,381.74