Finding the Fourth Proportional to 1,091.21, 1,505.61 and 666.05

Step by Step Solution

1. Step 1: Write the proportion equation
   1,091.21 : 1,505.61 = 666.05 : x
2. Step 2: Convert to fraction form
   1,091.21/1,505.61 = 666.05/x
3. Step 3: Cross multiply
   1,091.21x = 1,505.61 × 666.05
4. Step 4: Simplify right side
   1,091.21x = 1,002,804.01
5. Step 5: Solve for x
   x = 1,002,804.01/1,091.21
6. Step 6: Final answer
   x = 918.99