Finding the Fourth Proportional to 1,071.72, 1,605.60 and 828.12

Step by Step Solution

1. Step 1: Write the proportion equation
   1,071.72 : 1,605.60 = 828.12 : x
2. Step 2: Convert to fraction form
   1,071.72/1,605.60 = 828.12/x
3. Step 3: Cross multiply
   1,071.72x = 1,605.60 × 828.12
4. Step 4: Simplify right side
   1,071.72x = 1,329,629.47
5. Step 5: Solve for x
   x = 1,329,629.47/1,071.72
6. Step 6: Final answer
   x = 1,240.65