Finding the Fourth Proportional to 1,188.18, 1,785.42 and 640.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,188.18 : 1,785.42 = 640.76 : x
2. Step 2: Convert to fraction form
   1,188.18/1,785.42 = 640.76/x
3. Step 3: Cross multiply
   1,188.18x = 1,785.42 × 640.76
4. Step 4: Simplify right side
   1,188.18x = 1,144,016.79
5. Step 5: Solve for x
   x = 1,144,016.79/1,188.18
6. Step 6: Final answer
   x = 962.83