Finding the Fourth Proportional to 1,111.51, 1,533.90 and 639.15

Step by Step Solution

1. Step 1: Write the proportion equation
   1,111.51 : 1,533.90 = 639.15 : x
2. Step 2: Convert to fraction form
   1,111.51/1,533.90 = 639.15/x
3. Step 3: Cross multiply
   1,111.51x = 1,533.90 × 639.15
4. Step 4: Simplify right side
   1,111.51x = 980,392.19
5. Step 5: Solve for x
   x = 980,392.19/1,111.51
6. Step 6: Final answer
   x = 882.04