Finding the Fourth Proportional to 1,056.88, 1,586.86 and 644.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,056.88 : 1,586.86 = 644.78 : x
2. Step 2: Convert to fraction form
   1,056.88/1,586.86 = 644.78/x
3. Step 3: Cross multiply
   1,056.88x = 1,586.86 × 644.78
4. Step 4: Simplify right side
   1,056.88x = 1,023,175.59
5. Step 5: Solve for x
   x = 1,023,175.59/1,056.88
6. Step 6: Final answer
   x = 968.11