GATE Overflow | Mock GATE | Test 1 | Question: 10

Question

If $A+B$ means $A$ is the brother of $B$, $A-B$ means A is the sister of $B$, $A \times B$ means $A$ is the father of $B$. Then which of the following means that $C$ is the son of $M$?

• A. $M-N \times C +F$
• B. $M \times N - C +F$
• C. $F-C+N \times M$
• D. $N+M - F \times C$

Comments

Option (b)

---

Can you explain me ???

---

M is father of N

N is sister of C       

C is brother of F .  << this means C is boy.

This entire phrase means that M is father of N,C and F where C is boy,N is girl and F's gender cannot be determined.

---

I dont know how to solve this. I just studied Operator Precedence of Compiler Design, and I saw this question, and many other questions generate in my mind, about whether to evaluate left to right? Or X has higher precedence or + or -

Answer 1

Answer is B

which of the following means that C is the son of M?

means M is the Father of C. (Here I am saying M is the Father of C because in question there is no context(or syntax) for mother) 

Also, A×B means A is the father of B (given in question) 

So it is very clear that for being M is the father of C, It will be like M × C 

Now if you will notice then other notations + and - for brother and sister (i.e. + and - denotes same level(siblings))

This is given option  M × N − C + F  which means  M is father of N, N is sister of C and C is brother of F. This implies M is father of C,N and F, also C,N and F are siblings. 

other options can be understood in same way. 

Comments

C is the son of M?

means M is the Father of C. (Here I am saying M is the Father of C because in question there is no context(or syntax) for mother) 

This conclusion is incorrect. It doesn't matter if the question lists the syntax for mother or not. The question doesn't even ask you to determine the gender of the parent. It just says that M is the parent of C, and C is a son and not a daughter.

 

This is given option  M × N − C + F  which means  M is father of N, N is sister of C and C is brother of F. This implies M is father of C,N and F, also C,N and F are siblings. 

Again, the information you give is sufficient, but the observations you draw are not.

M is a parent of C. Correct and useful.

C, N, F are siblings. Correct and useful.

C is the brother of F. This is the piece of info you missed. It is useful because it determines the gender of C as a boy, hence making C a "son" of M.