IMO D . 28

( 2x + 2 / 5x ) = 1/2

=> x = 4

2x + 5x = 28

Simple logic took out A through C. 28 worked out. Answer: D

May not be academic, but is probably what most do on the test. :/

sanju09 wrote:In a certain calculus class, the ratio of the number of mathematics majors to the number of students who are not mathematics majors is 2 to 5. If 2 more mathematics majors were to enter the class, the ratio would be 1 to 2. How many students are in the class?
(A) 10
(B) 12
(C) 21
(D) 28
(E) 35



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as the ratio of no. of students who have mathematics as a major to the students who don't have mathematics as a major is 2 :5; therefore students having mathematics as a major would be (2/7)x where x is total no. of students.

as the total no. of students i.e. x must be multiple of 7 therefore option a,b are straight away out. left with option c,d,e as we see when two more students joins ratio becomes 1:3 the only option which satisfy this condition is D hence correct answer is D