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If ab is divisible by c, which of the following cannot be t
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07 Aug 2017, 13:08
07 Aug 2017, 13:08
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If ab is divisible by c, which of the following cannot be true?
A. a is divisible by c.
B. a is not divisible by c.
C. c is a prime number.
D. ab + c is odd and c is odd.
E. ab + c is odd and c is even.
Re: If ab is divisible by c, which of the following cannot be t
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10 Jan 2018, 00:21
10 Jan 2018, 00:21
1
This can be solved by substituting values for a,b and c.
For options A
Lets consider a =4, b=1 and c=2
now a is divisible by c. This is possible
For option B
Lets consider a =1, b=4 and c=2
now a is not divisible by c. This is possible
For option C
in the above two examples c is a prime number (c=2). Thus this is possible
For option D and E
let us consider a = 2, b=3 and c = 3
Now ab+c = 2*3 + 3 = 9 which is odd but c is odd as well. In no case can ab+c be odd and c be even.
Thus D is possible while E is not.
Hence E is the answer.
For options A
Lets consider a =4, b=1 and c=2
now a is divisible by c. This is possible
For option B
Lets consider a =1, b=4 and c=2
now a is not divisible by c. This is possible
For option C
in the above two examples c is a prime number (c=2). Thus this is possible
For option D and E
let us consider a = 2, b=3 and c = 3
Now ab+c = 2*3 + 3 = 9 which is odd but c is odd as well. In no case can ab+c be odd and c be even.
Thus D is possible while E is not.
Hence E is the answer.
Re: If ab is divisible by c, which of the following cannot be t
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22 Feb 2018, 18:19
22 Feb 2018, 18:19
2
answer: E
ab is an integer which a is the tens digit and b is a unit digit. It is divisible by c so:
ab / c = x and (c * x) = ab
now we try to find a condition for each of the options to be true
A: a= 30 and c = 3. Then a is divisible by c.
B: a= 12 and c=4. Then a is not divisible by c.
C: a= even and c=2. Then c is prime.
D: ab=30 and c=3. Then both ab+c=33 and c are odd. In the other words:
(ab+c)= (c*x+c)= c*(x+1) if x is even and c is odd then ab+c is odd and it’s possible.
F: as said in D, ab+c = c*(x+1). If ab+c is odd then c*(x+1) is odd. It means that c is odd and x is even. So it is impossible for c to be even when ab+c is odd.
ab is an integer which a is the tens digit and b is a unit digit. It is divisible by c so:
ab / c = x and (c * x) = ab
now we try to find a condition for each of the options to be true
A: a= 30 and c = 3. Then a is divisible by c.
B: a= 12 and c=4. Then a is not divisible by c.
C: a= even and c=2. Then c is prime.
D: ab=30 and c=3. Then both ab+c=33 and c are odd. In the other words:
(ab+c)= (c*x+c)= c*(x+1) if x is even and c is odd then ab+c is odd and it’s possible.
F: as said in D, ab+c = c*(x+1). If ab+c is odd then c*(x+1) is odd. It means that c is odd and x is even. So it is impossible for c to be even when ab+c is odd.
