Divisibility by 5

Divisibility by 5

A number is divisible by 5, if the digit at units place is either 0 or 5.

METHOD
Step 1. Check out the units digit of the number
Step 2. If the units digits is 0 or 5, then the number is divisible by 5.

Example 1. Consider 30
Step 1. Units digit is 0
Since the units digit is 0, 30 is divisible by 5
Check. 30 / 6 = 5 exactly

Example 2. Consider 295
Step 1. Units digit is 5
Since the units digit is 5, 295 is divisible by 5
Check. 295 / 5 = 59 exactly

Example 3. Consider 5948
Step 1. Units digit is 8, which is not 0 or 5
Since the units digit is not 0 or 5, 5948 is not divisible by 5
Check. 5948 / 5 = 1189 remain 3

Divisibility by 5

Number	Step 1	Units digit is 0 or 5?	Number Divisible by 5?
30	0	Yes	Yes
295	5	Yes	Yes
5948	8	No	No

Squaring 2-digit numbers ending in 5

Squaring 2-digit numbers ending in 5

The answer for the square has either 3 or 4 digits.
The last 2 digits of the answer is 25.

METHOD
Step 1. Add 1 to the tens digit.
Step 2. Multiply the sum rom Step 1 by the original tens digit value giving the leftmost digits for the square.
Step 3. Combine the product from Step 2 with 25.

Squaring 2-digit numbers ending in 5

Number	Tens digit	Step 1	Step 2	Step 3
15 x 15	1	1 + 1 = 2	2 x 1 = 2	2 25
25 x 25	2	2 + 1 = 3	3 x 2 = 6	6 25
35 x 35	3	3 + 1 = 4	4 x 3 = 12	12 25
45 x 45	4	4 + 1 = 5	5 x 4 = 20	20 25
55 x 55	5	5 + 1 = 6	6 x 5 = 30	30 25
65 x 65	6	6 + 1 = 7	7 x 6 = 42	42 25
75 x 75	7	7 + 1 = 8	8 x 7 = 56	56 25
85 x 85	8	8 + 1 = 9	9 x 8 = 72	72 25
95 x 95	9	9 + 1 = 10	10 x 9 = 90	90 25