GRE Sample Test 1 Quantitative Reasoning 1

Use the Group formula: Total = Group1 + Group2 − Both + Neither. In this problem, the total is 2,400. The question also states that 1,200 students (half of the total) take calculus, so that is Group1; one-third of that group (400) take both calculus and English.
Because every student takes calculus or English or both, the Neither group is zero. Solve for the number of students who take English by plugging these numbers into the group formula: 2400 = 1200 + Group2 − 400. The number of students who take English is 1,600, or (D).