A student received the following marks in the five of the six courses: 91, 86, 81, 79 and 92. Average of his marks in six subjects is 85. How many marks did he receive in the sixth subject?

A student received the following marks in the five of the six courses: 91, 86, 81, 79 and 92. Average of his marks in six subjects is 85. How many marks did he receive in the sixth subject?

Answer:

Let mark for 6th subject is X, then

Average mark = (91 + 86 + 81 + 79 + 92 + X) / 6 = 85

That is (429 + X) / 6 = 85

429 + X = 510

X = 81

So, marks he received in the sixth subject is 81.