CAT Remainders Questions
Master CAT Remainders Questions with practice questions and detailed solutions.
Question 1.
When $10^{100}$ is divided by 7, the remainder is
When $10^{100}$ is divided by 7, the remainder is
Text Explanation:
To find the value of $10^{100}mod\left(7\right)$
When 10 is divided by 7, it leaves a remainder 3, so the above equation can be written as,
$3^{100}mod\left(7\right)$
Now looking at the cyclicality of powers of 3 when divided by 7,
$3^1$ mod $7=3$
$3^2$ mod $7=2$
$3^3$ mod $7=6$
$3^4$ mod $7=4$
$3^5$ mod $7=5$
$3^6$ mod $7=1$
From this calculation, it is evident that the powers of 3 modulo 7 repeat every 6 steps. This forms a cycle: 3, 2, 6, 4, 5, 1
$3^{100}=\left(3^6\right)^{16}\times\ \left(3^4\right)$
Since $3^6$ mod $7=1$
We just need to consider $3^4$ mod $7$ which equals 4
Hence the answer is 4.
Question 2.
When $3^{333}$ is divided by 11, the remainder is
When $3^{333}$ is divided by 11, the remainder is
Text Explanation:
There are multiple ways of solving these sorts of questions. One method is to look for powers of the term in the numerator that leave a remainder of 1 or -1 when divided by the denominator.
Noting down the powers of 3, 3, 9, 27, 81, 243
243 is one such number, 242 is multiple of 11 (11 times 22), hence 243 will leave a remainder of 1 when divided by 11.
243 is 3 raised to power 5; we can rewrite the given term as $\dfrac{3^{330}\times\ 3^3}{11}$
The overall remainder will be $\left[\dfrac{3^{330}}{11}\right]_R\times\ \left[\dfrac{3^3}{11}\right]_R$
$\left[\dfrac{3^{5\times\ 66}}{11}\right]_R\times\ \left[\dfrac{3^3}{11}\right]_R$
$\left[\dfrac{243^{66}}{11}\right]_R\times\ \left[\dfrac{3^3}{11}\right]_R$
$1^{66}\times\ \left[\dfrac{27}{11}\right]_R$
$1\times\ 5$
$5$
Therefore, Option A is the correct answer.
Question 3.
If $10^{68}$ is divided by 13, the remainder is
If $10^{68}$ is divided by 13, the remainder is
Text Explanation:
There are multiple ways of solving such questions involving remainders; one easy way is to look for a power of numerator that leaves a remainder of 1 or -1 when divided by the denominator.
In this instance, 1000, when divided by 13, leaves a remainder of -1
We can rewrite the numerator as $\frac{10^{66}\times\ 100}{13}$
The remainder would be $\left[\frac{10^{66}}{13}\right]_R\times\ \left[\frac{100}{13}\right]_R$
$\left(-1\right)^{22}\times\ 9$
9
Therefore, Option C is the correct answer.
Question 4.
How many of the integers 1, 2, … , 120, are divisible by none of 2, 5 and 7?
How many of the integers 1, 2, … , 120, are divisible by none of 2, 5 and 7?
Text Explanation:
The number of multiples of 2 between 1 and 120 = 60
The number of multiples of 5 between 1 and 120 which are not multiples of 2 = 12
The number of multiples of 7 between 1 and 120 which are not multiples of 2 and 5 = 7
Hence, number of the integers 1, 2, … , 120, are divisible by none of 2, 5 and 7 = 120 - 60 - 12 - 7 = 41
Question 5.
Text Explanation:
$2^x + 2$ = 1 + 2 = 3 Which is divisible by 3. Hence, x = 0 is one possible solution.
At $x = 1, 2^x = 2$ which is in the given range [0.25, 200]
$2^x + 2$ = 2 + 2 = 3 Which is divisible by 4. Hence, x = 1 is one possible solution.
At $x = 2, 2^x = 4$ which is in the given range [0.25, 200]
$2^x + 2$ = 4 + 2 = 6 Which is divisible by 3. Hence, x = 2 is one possible solution.
At $x = 3, 2^x = 8$ which is in the given range [0.25, 200]
$2^x + 2$ = 8 + 2 = 3 Which is not divisible by 3 or 4. Hence, x = 3 can't be a solution.
At $x = 4, 2^x = 16$ which is in the given range [0.25, 200]
$2^x + 2$ = 16 + 2 = 18 Which is divisible by 3. Hence, x = 4 is one possible solution.
At $x = 5, 2^x = 32$ which is in the given range [0.25, 200]
$2^x + 2$ = 32 + 2 = 34 Which is not divisible by 3 or 4. Hence, x = 5 can't be a solution.
At $x = 6, 2^x = 64$ which is in the given range [0.25, 200]
$2^x + 2$ = 64 + 2 = 66 Which is divisible by 3. Hence, x = 6 is one possible solution.
At $x = 7, 2^x = 128$ which is in the given range [0.25, 200]
$2^x + 2$ = 128 + 2 = 130 Which is not divisible by 3 or 4. Hence, x = 7 can't be a solution.
At $x = 8, 2^x = 256$ which is not in the given range [0.25, 200]. Hence, x can't take any value greater than 7.
Therefore, all possible values of x = {0,1,2,4,6}. Hence, we can say that 'x' can take 5 different integer values.
Question 6.
Text Explanation:
= $(16 + 19)(16^2 - 16 * 19 + 19^2) + (17 + 18)(17^2 - 17 * 18 + 18^2)$ = 35 × odd + 35 × odd = 35 × even = 35 × (2k)
=> x = 70k
=> Remainder when divided by 70 is 0.
Instructions
Instructions
For the following questions answer them individually
For the following questions answer them individually
Question 7.
Let $n!=1*2*3* ...*n$ for integer $n \geq 1$.
If $p = 1!+(2*2!)+(3*3!)+... +(10*10!)$, then $p+2$ when divided by 11! leaves a remainder of
If $p = 1!+(2*2!)+(3*3!)+... +(10*10!)$, then $p+2$ when divided by 11! leaves a remainder of
Text Explanation:
Question 8.
Text Explanation:
So, $2^{256} = (-1)^{64}$(mod $17$)
$= 1$ (mod $17$)
Hence, the answer is 1. Option a).
Question 9.
Text Explanation:
Let k = 1; the number becomes 53
If it is divided by 84, the remainder is 53.
Option d) is the correct answer.
Alternative Solution.
Consider only for 3 and 4 and the remainders are 2 and 1 respectively.
So 5 is the first number to satisfy both the conditions. The number will be of the form 12k+5. Put different integral values of k to find whether it will leave remainder 5 when divided by 7. So the first number to satisfy such condition is 48x4+5= 53
Question 10.
Text Explanation:
Option d) is the correct answer.
Question 11.
Text Explanation:
So$a^2-a$ = b($b^3-2b^2-b+2$) . = (b - 2)(b - 1)( b)(b + 1)
The above given is a product of 4 consecutive numbers with the lowest number of the product being 2(given b >= 4)
In any set of four consecutive numbers, one of the numbers would be divisible by 3 and there would be two even numbers with the minimum value of the pair being (2,4).
Thus, for any value of b >=4, $a^2-4$ would be divisible by 3 x 2 x 4 = 24.
Thus, option C is the right choice. Options A and B are definitely wrong as a set of four consecutive numbers need not always include a multiple of 5 eg:(6,7,8,9)
Question 12.
Text Explanation:
Question 13.
Text Explanation:
There is one more method through which we can find the answer. Since we have to find even numbers, consider the numbers which are divisible by 14, 18 and 126 between 100 and 200. These are 7, 6 and 1 respectively.
Question 14.
Text Explanation:
Question 15.
Text Explanation:
5*7*9 mod 12 = 11 * 9 mod 12 = 99 mod 12 = 3
Question 16.
Text Explanation:
The number that divides both these numbers must be a factor of 1535.
307 is the only 3 digit integer that divides 1535.
Question 17.
Text Explanation:
Remainder when $55^3$ is divided by 3 = 1
Remainder when $17^3$ is divided by 3 = -1
Remainder when $72^3$ is divided by 3 = 0
So, $55^3 + 17^3 - 72^3$ is divisible by 3
So, the answer is d) 3 and 17
Question 18.
Text Explanation:
$7^{84}$ = $(7^3)^{28}$ = $343^{28}$
$343^{28}$ mod 342 = $1^{28}$ mod 342 = 1
Question 19.
Text Explanation:
N = (899K + 63) or N = ($29 \times 31$K) + 63
So when it is divided by 29, remainder will be $\frac{63}{29}$ = 5


