Multiplying two numbers ending with 5

There is a easy and quick way to find out the product of two numbers ending with 5.

Let us take an example

45 X 85

 
Step 1 : 4 + 8 = 12 ( Sum of the digits of two numbers leaving the last digit)
Since 12 is an even number write 25 in the answer.

                                  Step 2 : 4 X 8 = 32  

                                 Step 3 :  (4+8)/2 = 6 ( Since the sum is         the even number we divide it by 2)

Step 4 :   32+6= 38

Write it together 3825.


Let us take another example

35 X 85

Step 1 : 3 + 8 = 11
              Since the sum of first two digits are odd write 75 in the answer.
Step 2 : 3 X 8 = 24

Step 3 : (3+8-1) / 2 = 5 ( Since the sum is the odd number, we deduct -1)

Step 4 : 24 + 5 =29

Write it together 2975