Finding the Fourth Proportional to 2,152.56, 2,970.60 and 1,221.20

Step by Step Solution

1. Step 1: Write the proportion equation
   2,152.56 : 2,970.60 = 1,221.20 : x
2. Step 2: Convert to fraction form
   2,152.56/2,970.60 = 1,221.20/x
3. Step 3: Cross multiply
   2,152.56x = 2,970.60 × 1,221.20
4. Step 4: Simplify right side
   2,152.56x = 3,627,696.72
5. Step 5: Solve for x
   x = 3,627,696.72/2,152.56
6. Step 6: Final answer
   x = 1,685.29