Question

A teacher wrote a question on the board to which

42.5
%
of the
40
students in her class could not give the correct answer.

What is the number of students who answered correctly?

Answer 1

100% - 42.5% = 57.5%
57.5% of the 40 students answered correctly.
57.5% of 40 = 0.575 × 40 = 23 students

Answer 2

23

Explanation:

find 10% = 4

quadruple it = 16

half 10% = 2

half it again = 1

2.5% = 1

40% = 16

1 + 16 = 17

take 17 off of 40 = 23