Finding the Fourth Proportional to 2,153.18, 2,971.42 and 1,221.50

Step by Step Solution

1. Step 1: Write the proportion equation
   2,153.18 : 2,971.42 = 1,221.50 : x
2. Step 2: Convert to fraction form
   2,153.18/2,971.42 = 1,221.50/x
3. Step 3: Cross multiply
   2,153.18x = 2,971.42 × 1,221.50
4. Step 4: Simplify right side
   2,153.18x = 3,629,589.53
5. Step 5: Solve for x
   x = 3,629,589.53/2,153.18
6. Step 6: Final answer
   x = 1,685.69