Finding the Fourth Proportional to 1,055.72, 1,580.50 and 615.63

Step by Step Solution

1. Step 1: Write the proportion equation
   1,055.72 : 1,580.50 = 615.63 : x
2. Step 2: Convert to fraction form
   1,055.72/1,580.50 = 615.63/x
3. Step 3: Cross multiply
   1,055.72x = 1,580.50 × 615.63
4. Step 4: Simplify right side
   1,055.72x = 973,003.22
5. Step 5: Solve for x
   x = 973,003.22/1,055.72
6. Step 6: Final answer
   x = 921.65