Basic Quantitative Example Question-02:
Question:
If a, b, c and d are consecutive integers, which of the following MUST be even?
A) ac
B) bd
C) ad
D) ab + c
E) bc + d
Solution:
Similar to previous question, avoid plugin and simply apply logical thinking.
According to first choice, both a and c are either even or odd. I.e. when a is even, then c must also be even; also when a is odd, then c must also be odd. So, the product of a and c could be an even or an odd. This shows that Choice A is not MUST be even.
Similar to first choice, the second choice also can be either even or an odd. Thus, Choice B is not MUST be even.
According to third choice, either a or d must be even, but not both simultaneously. That is, if a is even then d must be odd and vice versa. So, the product of a and d must be even. Thus, Choice C MUST be even.
According to fourth choice, the product of a and b would always be even, but c might be even or an odd. So we cannot confirm whether fourth choice is even or odd. Thus, Choice D is not MUST be even.
Similarly, according to fifth choice, the product of b and c would always be even, but d might be even or an odd. So we cannot confirm whether fourth choice is even or odd. Thus, Choice E is not MUST be even.
In order to see another example, click on the “Example Question-03” button below: