Finding the Fourth Proportional to 1,617.79, 2,426.69 and 643.89

Step by Step Solution

1. Step 1: Write the proportion equation
   1,617.79 : 2,426.69 = 643.89 : x
2. Step 2: Convert to fraction form
   1,617.79/2,426.69 = 643.89/x
3. Step 3: Cross multiply
   1,617.79x = 2,426.69 × 643.89
4. Step 4: Simplify right side
   1,617.79x = 1,562,521.42
5. Step 5: Solve for x
   x = 1,562,521.42/1,617.79
6. Step 6: Final answer
   x = 965.84