Finding the Fourth Proportional to 1,274.64, 1,756.80 and 978.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,274.64 : 1,756.80 = 978.72 : x
2. Step 2: Convert to fraction form
   1,274.64/1,756.80 = 978.72/x
3. Step 3: Cross multiply
   1,274.64x = 1,756.80 × 978.72
4. Step 4: Simplify right side
   1,274.64x = 1,719,415.30
5. Step 5: Solve for x
   x = 1,719,415.30/1,274.64
6. Step 6: Final answer
   x = 1,348.94