Question

Question 10 Determine if 25110 is divisible by 45. [Hint: 5 and 9 are co-prime numbers. Test the divisibility of the number by 5 and 9].

Class 6 - Math - Playing with Numbers Page 62

Answer 1

To Check whether 25110 is divisible by 45 

As we know factors of 45 = 3×3×5 

So, if 25110 is divisible by , it must be divisible by all factors of 45 also , So factors of 45 are (3,3,5).

We will check the divisibility of 25110 by 3 and 5 .

Divisibility of 25110 by 3

if a number is divisible by 3 then sum of digits of that number must be divisible by 3.

2+5+1+1+0 = 9 
⇒ 25510 is divisible by 3.

Divisibility by 5
If a number ends with 0 or 5 , then that number is divisible by 5.

25110 ends with 0 
⇒25110 is divisible by 5.

If 25110 is divisible by 3 and 5 , then it is divisible by 45 also.
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Answer 2

Hey there !!!!

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To check if 25110 is divisible by 45  :-

45= 5*9

9=3*3

25110 will be divisible by 45 if it is divisible by 5 and 3.

Divisibility check for 5:

A number is said to be divisible by 5 if it ends with 0 or 5 

25110 ends with 0 .

So, 25110 is divisible by 5.

Divisibility check for 9:

9= 3*3

3 is a factor of 9

So, divisibility rules for 9 will be same as that of 3.

Sum of digits in 25110 = 2+5+1+1+0=9

So, 25110 is divisible by 9.

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Hope this helped you.........