Finding the Fourth Proportional to 1,231.72, 1,700.38 and 840.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,231.72 : 1,700.38 = 840.80 : x
2. Step 2: Convert to fraction form
   1,231.72/1,700.38 = 840.80/x
3. Step 3: Cross multiply
   1,231.72x = 1,700.38 × 840.80
4. Step 4: Simplify right side
   1,231.72x = 1,429,679.50
5. Step 5: Solve for x
   x = 1,429,679.50/1,231.72
6. Step 6: Final answer
   x = 1,160.72