Raj scored 67, 69, 78, and 88 in 4 of his subjects. What should be his score in the 5th subject so that his average equals 80?

Let the score in 5th subject be x

⇒ Total score = 67 + 69 + 78 + 88 + x = 302 + x

⇒ Average = total marks/total subject

⇒ 80 = (302 + x)/5

⇒ 400 = 302 + x

⇒ x = 98

∴ score in 5th subject should be 98