Finding the Fourth Proportional to 1,218.51, 1,681.56 and 687.42

Step by Step Solution

1. Step 1: Write the proportion equation
   1,218.51 : 1,681.56 = 687.42 : x
2. Step 2: Convert to fraction form
   1,218.51/1,681.56 = 687.42/x
3. Step 3: Cross multiply
   1,218.51x = 1,681.56 × 687.42
4. Step 4: Simplify right side
   1,218.51x = 1,155,937.98
5. Step 5: Solve for x
   x = 1,155,937.98/1,218.51
6. Step 6: Final answer
   x = 948.65