Finding the Fourth Proportional to 1,182.72, 1,772.64 and 840

Step by Step Solution

1. Step 1: Write the proportion equation
   1,182.72 : 1,772.64 = 840 : x
2. Step 2: Convert to fraction form
   1,182.72/1,772.64 = 840/x
3. Step 3: Cross multiply
   1,182.72x = 1,772.64 × 840
4. Step 4: Simplify right side
   1,182.72x = 1,489,017.60
5. Step 5: Solve for x
   x = 1,489,017.60/1,182.72
6. Step 6: Final answer
   x = 1,258.98