Finding the Fourth Proportional to 1,015.20, 1,401.20 and 661.12

Step by Step Solution

1. Step 1: Write the proportion equation
   1,015.20 : 1,401.20 = 661.12 : x
2. Step 2: Convert to fraction form
   1,015.20/1,401.20 = 661.12/x
3. Step 3: Cross multiply
   1,015.20x = 1,401.20 × 661.12
4. Step 4: Simplify right side
   1,015.20x = 926,361.34
5. Step 5: Solve for x
   x = 926,361.34/1,015.20
6. Step 6: Final answer
   x = 912.49