DIVISIBILITY ( POST 5)

Good morning Boys, 
Let us Revise Test of divisibility for 3.

If the sum of the digits is divisible by 3, then the number is divisible by 3.
 on the bases of this we are going to tackle Q5 on page 57.

Q5. Write the smallest digit and the greatest digit in the blank space of each of the following numbers so that the number formed is divisible by 3.

a. __6724
On adding 6+7+2+4 = 19.

take 3 X 7 = 21 closest to 19 and then,
Subtract.

21-19=2
So, 2 is the smallest number added to 6724 to make it divisible by 3.
_2__6724.

Now, add the greatest number to 6724 to make it divisible by 3.
__6724
6+7+2+4=19.

Suppose 3 X 9=27,
27-19=8.
Therefore, we now put 8 in the blank to make ___6724 divisible by 3.
You may now attempt Q5b on your own .

We now come to test of  divisibility of 11.

Having watched the above video you may now attempt 2 sums.,

1. 16682
2.1331

DIVISIBILITY BY 11

RULE- Subtract the last digit from the number formed by the remaining digits.

Example- Is 396 divisible by 11?

 39-6 = 33

since 33 is divisible by 11 , so 396 if divisible by 11.

Open to Q6 on page 58.
Q1. Write a digit in the blank space in each of the following numbers so that the number formed is divisible by 11.

a. 92__389.

Method to solve.
92__398.

Take the sum of the digits in the odd place from the right.
9+__+8=17

Now, find the sum of the digits in the even place from the right.
2+3+9=14.

On subtracting
17-14=3,         
3 is added in the blank to make the number divisible by 11.

you may now do Q6 b page 58 for homework.

A QUICK RECAP OF   RULES OF DIVISIBILITY

THANK YOU have a good day.