Finding the Fourth Proportional to 1,315.40, 1,969.43 and 664.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,315.40 : 1,969.43 = 664.76 : x
2. Step 2: Convert to fraction form
   1,315.40/1,969.43 = 664.76/x
3. Step 3: Cross multiply
   1,315.40x = 1,969.43 × 664.76
4. Step 4: Simplify right side
   1,315.40x = 1,309,185.12
5. Step 5: Solve for x
   x = 1,309,185.12/1,315.40
6. Step 6: Final answer
   x = 995.28