Counting by fives means adding five to previous number or jump by 5.
Each number is 5 more than the previous number. if the 1st number is **an odd** number then the next number by adding 5 will be **an even** number. And if the 1st number is **an even** number then the next number will be **an odd** number. So counting by five's gives you alternatively odd and even numbers.

**Example: Counting by 5's**

If the 1st number is 8 then next 5 numbers obtained by counting by 5's are; 8, 8 + 5 =**13**; 13 + 5 =**18**; 18 + 5 =**23**; 23 + 5 = **28**; 28 + 5 =**33**

So next 5 numbers after 8 are **13,18,23,28,33**.

**Example 1 :** Find the next 3 numbers after 21 by counting it by 5's.

Solution : 1st number = **21 + 5 = 26**

2nd number = **26 + 5 = 31**

3rd number = **31 + 5 = 36**

So next 3 numbers after 21 are : **26,31,36**.

**Example 2 :** Find the missing numbers. 15,20,____,____,____,____.

Solution : 1st number is 15 and next number is 20 so from this we can see that its counting by 5's

. That means after adding 5 to previous number we will get the next number. So,

1st missing number = 20 + 5 =25

2nd missing number = 25 + 5 = 30

3rd missing number = 30 + 5 = 35

4th missing number = 35 + 5 = 40

So the number are 15,20,**25,30,35,40**.

**Example 3 :** Complete the following pattern.

12,17,22,____,____,____

**Solution :** In 12,17 and 22 the gap of 5. That means by adding 5 we get a next number. So, 1st missing number is 22 + 5 = **27**, 2nd missing number is 27 + 5 =**32** and 3rd missing number is 32 + 5 = **37**. Series is 12,17,22,**27,32,37.**

**Practice**

Q.1 Find the missing numbers.

1) 27,32,___,___,___,___,___,62

2) 61,66,___,___,81,___,___,

3) 51,___,61,65,___,___,___,

4) 84,___, 94,99,___

5) ,___,20,25,___,35,___

2nd Grade Math

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