GATE2019 IN: GA-4

Question

Five numbers $10,7,5,4$ and $2$ are to be arranged in a sequence from left to right following the directions given below:

1. No two odd or even numbers are next to each other.
2. The second number from the left is exactly half of the left-most number.
3. The middle number is exactly twice the right-most number.

Which is the second number from the right?

• A. $2$
• B. $4$
• C. $7$
• D. $10$

Answer 1

1. No two odd or even numbers are next to each other.
2. The second number from the left is exactly half of the left-most number.
   So, the left most number must be even and its half must be odd which comes next. Only options are $10,5$
3. The middle number is exactly twice the right-most number.
   Middle number must be even and only options left are $2$ and $4$. Since $1$ is not there, $4$ must be the middle and $2$ the right most. 

Thus we get $$10\quad 5 \quad 4 \quad 7 \quad 2$$

Required answer is $7.$

Option C.

Comments

Actually to answer the question, statement 1 and 2 are sufficient

Answer 2

From the above possible instructions, the sequence possible is:- 10,5,4,7,2.

So, the answer is:- 7