The average of 13 results is 60. If the average of the first seven results is 59 and that of the last seven is 62 , the 7th no. is :

67

Average  of 13 results = 60

⇒ Sum of these 13 results = 780

Sum of first seven numbers = 59 × 7 = 413

Sum of last seven numbers = 62 × 7 = 434

∴ 7th number = Sum of first seven numbers + Sum of last seven numbers − Sum of all numbers

7th number  = 413 + 434 – 780 = 67