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HCF and LCM

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How many pairs of natural numbers exist such that their greatest common divisor is 45 and product is 21600?

 

 

 
TG Team 18/11/2018 12:24 pm

45a x 45b = 21600

ab = 21600/45

Which is not possible as a, and b are positive integers . 

 

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Three runners running around a circular track can complete one revolution in 2,4and 5.5 hours respectively. When will they meet at the starting point? 

TG Team 15/01/2019 12:57 pm

First runner reaches the starting point every two hour 

Second runner reaches the starting point every four hour 

The third runner reaches the starting point every 5.5 

So just take LCM of 2 , 4 and 5.5 🙂 

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A rectangular cloth measuring 54 cm *90cm has tobe cut into equal squares such that no cloth is wasted. What is the least number of squares that can be made? 

TG Team 16/01/2019 1:58 pm

Hi Nancy 

Take the HCF of 54 and 90. 

HCF ( 54 and 90) = 18 

So we can put 54/18 i.e 3 square tiles in one direction and 90/18 i.e 5 square tiles in another direction . 

Total : 5 x 3 = 15 square tiles 

TG Team 16/01/2019 2:04 pm

Alternate Approach : 

For least number of tiles side of the square tiles should be maximum. 

side of the square = HCF (54, 90) = 18 

Number of squares = (Area of the floor )/ (Area of a tile) = (54 x 90)/ ( 18 x 18) = 15 

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A number N is divisible by 10,90,98,882 but it is not divisible by 50or 270 or 686 or 1764. It os also known that N is a factor of 9261000. What is N? 

TG Team 16/01/2019 1:53 pm

Use option - elimination. 

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P and Q are two disticnt whole no. And p+1,p+2,p+3,.......p+7 are integral multiples of q+1,q+2,q+3,.......q+7 Respectively. What is the minimum value of P? 

TG Team 16/01/2019 2:29 pm

For minimum p, q should be minimum that is 0.  

so p +1 will be divisible by  1 , 
p + 2 will be  divisible by 2 , p + 3 will be divisible by 3  and so on ....

Hence , just take LCM of 1, 2 , 3, 4....., 7 i.e 420

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Great thanks to share here, amazing platform for the maths question.

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Which is the largest six digits number, which when divided by 12, 15, 20, 24 and 30, leaves the remainder 8, 11, 16, 20 and 26 respectively.

(a) 999956               (b) 999960               (c) 999964               (d) 999982

Neraj (TG) 28/04/2024 5:47 pm
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Let x be the greatest number which when divided by 955, 1027, 1075, the remainder in each case is the same. Which of the following is NOT a factor of x?

(a) 6                            (b) 16                         (c) 4                            (d) 8

Neraj (TG) 28/04/2024 5:49 pm

@neha-singh 

To find the value of x, we need to find the HCF of the difference between all the three given numbers.

1027 - 955 = 72, 1075 – 1027 = 48

HCF of (72 and 48) = 24

Factors of 24 = 1, 2, 3, 4, 6, 8, 12, 24

Hence, 16 is not the factor of x

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When 1062, 1134 and 1182 are divided by the greatest number x, the reminder in case is y. What is the value of (x-y)?

(a) 19                         (b) 17                         (c) 16                         (d) 18

Neraj (TG) 28/04/2024 5:49 pm

@neha-singh 

To find the required greatest number, we need to find the HCF of the difference between all the three given numbers.

1134 - 1062 = 72, 1182 - 1134 = 48

HCF of 72 and 48 = 24

Now, When 1062 is divided by 24 leaves, remainder 6.

So, x - y = 24 - 6 = 18

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What is the sum of the digits of the least number which when divided by 15, 18 and 36 leaves the same remainder 9 in each case and is divisible by 11?

(a) 18                         (b) 16                         (c) 17                         (d) 15

Neraj (TG) 28/04/2024 5:50 pm

@neha-singh 

LCM of (15,18,36) = 180

Number can be written as 180k + 9, which is divisible by 11.

Now, putting K = 6 we get:

180 × 6 + 9 = 1080 + 9 = 1089

Hence, required sum = 1+0+8+9 = 18

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A gardener planted 1936 saplings in a garden such that there were as many rows of saplings as the columns. The number of rows planted is:

(a) 46                         (b) 44                         (c) 48                         (d)42

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4 bells toll together ay 9 am. they toll after 7,8 11,12 seconds resp. how many times will they toll together again in the next 3 hrs.?

a) 3

b)4

c)5

d)6

TathaGat 02/06/2024 5:07 pm

@lydiamadini 

Please find the solutions below. 

1. The LCM of the individual intervals will give the time at which all the bells will ring together. Which is LCM(7,8,11,12) = 1848sec  so the bells would ring together every 1848 secs.

In 3 hours, they would ring (3x60x60)/1848 = 5.8

Thus the bells will toll together 5 times in next 3 hours.'

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