1)If p,q,r are positive integers such that p<q<r,then what is the maximum possible value of GCD of p,q,r.?
A)p
B)q
C)r
D)1
E)p*q*r
I love this sum. It is pure concept. We will go by one by one options
1 can be GCD if P Q R is Co – prime to each other.
P*Q*R – can be LCM, but never a GCD.
Within P,Q,R – only the smallest number can be GCD – to understand this you may chose 3 numbers. Write them in their canonical form. From that to find GCD we will take common factors with their lowest power, so the small number P only can be GCD.
2)If x and n are positive integers then the number of prime factors of nx will always be greater than or equal to the number of prime factors of x^n?
A)True
B)False
C)cannot be determined
I am not sure how to explain this, but I choose few numbers and tested. It is always true.
3)If p,q,r are positive integers such that p<q<r,then what is the minimum possible value of LCM of p,q,r.?
A)p
B)q
C)r
D)1
E)p*q*r
Same as first qs.
P*q*r is maximum LCM possible
R is the minimum LCM possible.
As I told early you can try it by the way I mentioned in first qs.
4. If P is cube of a prime number, then how many factors does P have?
The number of factors can be found by adding one to the power. So four in this case.
Another example how to find factors: 23 * 32 = (3+1) * (2+1) = 4*3 =12 factors
5)If P and Q are Prime numbers then Q^5+P*Q is always even?
Interesting one, the problem in the sum is with prime number 2. If they say p and Q are >2 then it would be different.