Of all the students at a coaching centre, 45% joined the morning batch. Of the students in the morning batch, 40% are girls. Girls in the morning batch are what per cent of all the students at the centre?

Take 100 students. The morning batch holds 45 of them, and 40% of 45 = 18 are girls, so the answer is 18%. 27% is 60% of 45 - the BOYS of the morning batch. 85% adds the two figures and 5% subtracts them; neither works, because the 40% must be taken OF the 45%, not alongside it.