percentage is a value by a fraction of 100.
120 marks is equivalent to 60%
this means from the whole amount, 60 % of the whole amount is 120 marks
we need to find the full marks
if 60 % --- 120
then 1 % --- [tex] \frac{120}{60} [/tex]
full marks are 100 %
therefore 100 % - [tex] \frac{120}{60} * 100 [/tex]
100 % --- 200 marks
full marks are 200 marks