The average of 11 results is 50. If the average of the first six results is 49 and that of the last six is 52, the sixth no. is :

56

Average  of 11 results = 50

⇒ Sum of these 11 results = 550

Sum of first six numbers = 49 × 6 = 294

Sum of last six numbers = 52 × 6 = 312

∴ Sixth number = Sum of first six numbers + Sum of last six numbers − Sum of all numbers

Sixth number  = 294 + 312 – 550 = 56