Finding the Fourth Proportional to 1,221.59, 1,685.76 and 690.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,221.59 : 1,685.76 = 690.50 : x
2. Step 2: Convert to fraction form
   1,221.59/1,685.76 = 690.50/x
3. Step 3: Cross multiply
   1,221.59x = 1,685.76 × 690.50
4. Step 4: Simplify right side
   1,221.59x = 1,164,017.28
5. Step 5: Solve for x
   x = 1,164,017.28/1,221.59
6. Step 6: Final answer
   x = 952.87