How the average mark is calculated
Average mark = Sum of all marks / Number of marks
Example. Marks 5, 4, 4, 3: (5 + 4 + 4 + 3) / 4 = 4.0. The final grade is 4.
How many 5s you need
For the average to reach the threshold, the sum of marks has to grow faster than their number. If the current sum is S with n marks and you need threshold T, the number of 5s k comes from the inequality:
(S + 5k) / (n + k) ≥ T → k ≥ (T × n − S) / (5 − T)
For marks 5, 4, 4, 3 and a threshold of 4.5: (4.5 × 4 − 16) / 0.5 = 4. You need four 5s in a row.
How term grades are given
There are no uniform rounding rules in Russia: each school sets them in its regulations on ongoing assessment. Most often 4.5 and above is a 5, 3.5–4.49 is a 4, and 2.5–3.49 is a 3. Many schools also weight marks: a test counts more than an answer at the board. If your electronic gradebook uses a weighted average, go by that.