Finding the Fourth Proportional to 1,142.98, 1,577.40 and 645.67

Step by Step Solution

1. Step 1: Write the proportion equation
   1,142.98 : 1,577.40 = 645.67 : x
2. Step 2: Convert to fraction form
   1,142.98/1,577.40 = 645.67/x
3. Step 3: Cross multiply
   1,142.98x = 1,577.40 × 645.67
4. Step 4: Simplify right side
   1,142.98x = 1,018,479.41
5. Step 5: Solve for x
   x = 1,018,479.41/1,142.98
6. Step 6: Final answer
   x = 891.08