MCQ Questions for Class 6 Maths Playing With Numbers Quiz 5

What is the value of

$x$ for which

$x, x + 1, x + 3$ are all prime numbers?

0%
$0$
0%
$1$
0%
$2$
0%
$101$

Explanation

Option

$A :$ Substitute

$x=0,$

$x,x+1,x+3=0,1,3$ are not prime numbers.

Option

$B :$ Substitute

$x=1,$

$x,x+1,x+3=1,2,4$ are not prime numbers.

Option

$C :$ Substitute

$x=2,$

$x, x + 1, x + 3=2,3,5$ which are all prime numbers.

Hence, option

$C$ is correct.

The smallest 3 digit prime number is:

0%
$101$
0%
$103$
0%
$109$
0%
$113$

Explanation

The smallest 3-digit number is

$100$ , which is divisible by

$2$ .

$\therefore$

$100$ is not a prime number.

$\sqrt{100}< 11$ and

$101$ is not divisible by any of the prime numbers

$2,3,5,7,11$ .

$\therefore$

$101$ is a prime number.
Hence

$101$ is the smallest 3-digit prime number.

Which of the following number is a prime?

0%
$667$
0%
$861$
0%
$481$
0%
$331$

Explanation

$667$ is divisible by

$23$

$861$ is divisible by

$3$

$481$ is divisible by

$13$

$331$ is divisible only by

$1$ and

$331$ .

$\therefore 331$ is a prime number.

Which of the following is a prime number?

0%
$33$
0%
$81$
0%
$93$
0%
$97$

Explanation

Clearly,

$97$ is a prime number.

Consider the following numbers.

$247$

$203$
Which of the above number is/are prime?

0%
$1$ only
0%
$2$ only
0%
Both $1$ and $2$
0%
Neither $1$ nor $2$

Explanation

A number which is divisible by itself and

$1$ are prime numbers.

$247 = 13\times 19$
2.

$203 = 7\times 79$

Here both the numbers have some divisors.
So, none of the two are prime.

Which one of the following is a prime number?

0%
$184$
0%
$171$
0%
$173$
0%
$221$

Explanation

$184 = 23\times 8$

Therefore, cannot be prime

$171 = 19\times 9$

Therefore,cannot be prime

$221 = 17\times 13$

Therefore, cannot be prime
Hence, by elimination we have

$173$ as a prime number.

Which one of the following is not a prime number?

0%
$31$
0%
$61$
0%
$71$
0%
$91$

Explanation

$91$ is divisible by

$7$ and

$13$ . So, it is not a prime number.

Rest all the given numbers are prime numbers since they don't have any factors other than

$1$ and themselves.

Find

$HCF$ by finding factors:

$16$ and

$56$ .

0%
$6$
0%
$18$
0%
$8$
0%
$9$

Explanation

The given numbers are

$16$ and

$56$

Factorizing the given numbers,

$16 = 2 \times 2 \times 2 \times 2$

$56 = 2 \times 2 \times 2 \times 7$

Since, the common factors are

$2,2,2$ , this implies that

$H.C.F = 2 \times 2 \times 2$

$=8$

Hence, the correct option is

$Op-C$ .

Find HCF of

$66$ and

$88$ .

0%
$21$
0%
$23$
0%
$24$
0%
$22$

Explanation

Factorization of the following

$66 = 1 \times 3 \times 2 \times 11$

$88 = 1 \times 2 \times 2 \times 2 \times 11$

Since, the common factor is

$1,2,11$ this implies that

$HCF=22$

Hince, the correct option

$D$

Find HCF of

$54, 81$ and

$99$ .

0%
$8$
0%
$9$
0%
$10$
0%
$11$

Explanation

Factorization of the following.

$54 = 2 \times 3 \times 3 \times 3$

$81 = 3 \times 3 \times 3 \times 3$

$99 = 3 \times 3 \times 11$

Since, the common factor is

$3 \times 3$ ,this implies that

$H.C.F = 3 \times 3$

Hence,the correct option

$B$ .

HCF of two co-prime number is _______.

0%
$1$
0%
$0$
0%
$2$
0%
None of these

Explanation

HCF of two co-prime numbers is

$1$ because they have only

$1$ as a common factor.

HCF of two or more prime numbers is ___________.

0%
$0$
0%
$2$
0%
$4$
0%
$1$

Explanation

HCF of two or more prime numbers is

$1$

Let us take an example,

$5$ and

$7$ both are prime numbers.

$5=1\times5$

$7=1\times7$

So, HCF

$=1$

Hence,

$Op-D$ is correct.

Which of the following numbers is prime?

0%
$119$
0%
$187$
0%
$247$
0%
$179$

Explanation

$119$ is divisible by

$7$

$187$ is divissible by

$11$

$247$ is divisible by

$13$

$179$ is not divisible by any number.

Hence

$179$ is a prime number.

$( 7 \times 11 \times 13 + 13 )$ is a/an

0%
Composite number
0%
Prime number
0%
Irrational number
0%
Imaginary number.

Explanation

$(7\times 11\times 13+13)=13\{(7\times11)+1\}=13\times 78=1014$

Since,

$1014$ is divided by

$13,78$ which is other than

$1$ and the number itself, so it is a composite number.

The co-prime numbers from the following pairs, are ______.

0%
7 and 63
0%
36 and 25
0%
35 and 29
0%
63 and 81

Explanation

If the H.C.F of two numbers are

$1$ they are said to be co-prime

(A) HCF (7, 63) = 7
(B) HCF (36, 25) = 1
(C) HCF (35, 29) = 1
(D) HCF (63, 81) = 9
So, 36 & 25 and 35 & 29 are co-prime numbers.

G.C.D of

$4$ and

$19$ is _________.

0%
$1$
0%
$4$
0%
$19$
0%
$76$

Explanation

There is no common factor between

$4$ and

$19$ . Hence, G.C.D. of

$4$ and

$19$ is

$1$ .

The reciprocal of the smallest prime number is _______.

0%
$0$
0%
$\dfrac {1}{2}$
0%
$1$
0%
$2$

Explanation

Prime no. are those which has only two factors.

One and the number itself.

$Note:$

$1$ is neither prime nor composite.

So, the smallest prime number is

$2$ .

Hence, reciprocal of

$2$

$= \dfrac{1}{2}$

Which of the following is not a prime number?

0%
$23$
0%
$29$
0%
$43$
0%
$21$

Explanation

Factors of

$23 = 23 \times 1$

Factors of

$29 = 29 \times 1$

Factors of

$43 = 43 \times 1$

Factors of

$21 = 3 \times 7$

So, ioption D

$23$ is not a prime number

The number

$111111111$ is a

0%
Prime number
0%
Composite number
0%
Divisible by $\frac{10^7-1}{9}$
0%
None of these

Explanation

A whole number that can be divided exactly by numbers other than 1 or itself is known as composite numbers.

111111111 is an odd composite number. It is composed of three distinct prime numbers multiplied together.

Prime factorisation of

$111111111 = {3}^{2} \times 37 \times 333667$

Which of the following numbers are co-prime?
a)

$18$ and

$35$
b)

$15$ and

$37$
c)

$30$ and

$415$
d)

$17$ and

$68$
e)

$216$ and

$215$
f)

$81$ and

$16$

0%
a,b and f
0%
a,b,e and f
0%
ab,c and f
0%
b,d and f

Explanation

Two numbers are co-prime, if the only positive integer that divides both of them is

$1$ . That is, their H.C.F.

$=1$

(a)

$18=1\times 2\times 3\times 3$

$35=1\times 5\times 7$

$H.C.F.=1$

So, the numbers are co-prime.

(b)

$15=1\times 3\times 5$

$37=1\times 37$

$H.C.F.=1$

So, the numbers are co-prime.

(c)

$30=1\times 2\times 3\times 5$

$415=1\times 5\times 83$

$H.C.F.=5$

So, the numbers are not co-prime.

(d)

$17=1\times 17$

$68=1\times 2\times 2\times 17$

$H.C.F.=17$

So, the numbers are not co-prime.

(e)

$216=1\times 2\times 2\times 2\times 3\times 3\times 3$

$215=1\times 5\times 43$

$H.C.F.=1$

So, the numbers are co-prime.

(f)

$16=1\times 2\times 2\times 2\times 2$

$81=1\times 3\times 3\times 3\times 3$

$H.C.F.=1$

So, the numbers are co-prime.

The total number of factors for

$50$ are

0%
$16$
0%
$6$
0%
$4$
0%
$10$

Explanation

No. of factors for

$50$

$50=5\times 5\times 2=5^2\times 2^1$

Total no. of factors are

$=(2+1)\times (1+1)=6$

How many two-digit prime numbers are there having the digit

$3$ in their units place?

0%
$10$
0%
$8$
0%
$6$
0%
$5$

Explanation

$2$ digit prime nos. having

$3$ in their units place are-

$13,23,43,53,73$

$\therefore$ There are

$5$ such nos.

The factor of 252 is:

0%
2
0%
5
0%
11
0%
10

Explanation

$252 = 2 \times 2 \times 3 \times 3 \times 7$ .

The prime factors of

$252$ are

$2,3,7$ .

Thus the answer will be A.

A number is divisible by

$9$ , if the sum of the digits of the number is divisible by _______ .

0%
$3$
0%
$9$
0%
$6$
0%
$2$

Explanation

A number is divisible by 9 if the sum of the digits of the number is divisible by 9.

For example

$81$ is divisible by

$9$ as

$8 + 1 = 9$ is divisible by

$9$ .

So, option B is correct.

A student was asked to find the sum of all the prime numbers between

$10$ and

$40.$ He found the sum as

$180.$ Which of the following statements is true?

0%
He missed one prime number between $10$ and $20$
0%
He missed one prime number between $20$ and $30$
0%
He added one extra prime number between $10$ and $20$
0%
None of these

Explanation

Prime numbers between

$10$ and

$40$ are

$11,13,17,19,23,29,31,37$
Sum of these prime numbers

$= 180$

$\therefore$ Option

$D$ is correct.

Which of the following is divisible by

$9$ ?

0%
$75636$
0%
$89321$
0%
$75637$
0%
$75632$

Explanation

Number are divisible by

$9$ if sum of the all the digits present in it , is divisible by

$9$ .

$(a)75636$

$\Rightarrow 7+5+6+3+6=27$ and

$27$ is divisible by 9.

Hence,

$75636$ is divisible by

$9$

$(b)89321$

$\Rightarrow 8+9+3+2+1=23$ and

$23$ is not divisible by

$9$ .

So,

$89321$ is not divisible by

$9$ .

$(c)75637$

$\Rightarrow 7+5+6+3+7=28$ and

$28$ is not divisible by

$9$ .

So,

$75637$ is not divisible by

$9$ .

$(c)75632$

$\Rightarrow 7+5+6+3+2=26$ and

$26$ is not divisible by

$9$ .

So,

$75632$ is not divisible by

$9$

Which of the following number is divisible by

$6$ ?

0%
$3792$
0%
$5634$
0%
$9832$
0%
$3684$

Explanation

The sum of the digits of the number should be divisible by

$3$ and the number should be even.

For option A:

$3 + 7+ 9+ 2 =21$ which is divisible by

$3$ and number is even. so answer A is right.

The sum of prime numbers, out of the numbers

$17, 8, 21, 13, 41, 2, 27, 31, 51$ is:

0%
$125$
0%
$102$
0%
$104$
0%
$155$

Explanation

Prime numbers out of

$17,8,21,13,41,2,27,31,51$ are

$17,13,41,2,31$ .

Sum of prime numbers

$= 17+13+41+2+31=104$ .

Which of the following numbers is divisible by

$9$ ?

0%
$8576901$
0%
$96345210$
0%
$67594310$
0%
none of these

Explanation

We use a rule to check whether the number is divisible by 9 or not.

A number is divisible by 9 if the sum of the digits is evenly divisible by 9.

Since sum of its digits

$= 8 + 5 + 7 + 6 + 9 + 0 + 1 = 36$

$36$ is divisible by

$9$
Option (a) is the correct answer

Which of the following numbers is divisible by

$9$ ?

0%
$972063$
0%
$730542$
0%
$785423$
0%
$561284$

Explanation

We use a rule to check whether the number is divisible by 9 or not.

A number is divisible by 9 if the sum of the digits is evenly divisible by 9.

Sum of digits

$= 9 + 7 + 2 + 0 + 3 = 27$ which is divisible by

$9$

CBSE Questions for Class 6 Maths Playing With Numbers Quiz 5 - MCQExams.com

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Practice Class 6 Maths Quiz Questions and Answers

CBSE Questions for Class 6 Maths Playing With Numbers Quiz 5 - MCQExams.com

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Practice Class 6 Maths Quiz Questions and Answers

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