Finding the Fourth Proportional to 1,187.52, 1,638.72 and 656.40

Step by Step Solution

1. Step 1: Write the proportion equation
   1,187.52 : 1,638.72 = 656.40 : x
2. Step 2: Convert to fraction form
   1,187.52/1,638.72 = 656.40/x
3. Step 3: Cross multiply
   1,187.52x = 1,638.72 × 656.40
4. Step 4: Simplify right side
   1,187.52x = 1,075,655.81
5. Step 5: Solve for x
   x = 1,075,655.81/1,187.52
6. Step 6: Final answer
   x = 905.80