Please follow carefully the solution that we have provided here below..Mathematics is generally simple and fantastic but the greater part of the world is scared even when you mention the word maths. Majority of those who shy away from maths are those who have been frightened by close friends who themselves run away from the subject. Many rarely give a third try if they try twice and fail. No one wants to be associated with failures but most often failures need to be smashed.

This problematic is not basically mathematics, it is logic! Though it is also an arithmetic sequence.. It’s so easy even a 5 year old can confidently squash it if probably understood. Now this is how this logic is resolved:

(1) 4+4=20

(2) 5+5=30

(3) 6+6=42

(4) 7+7=56

Then

(6) 9+9=

To get this answer you need to know the missing sequence which is (5) 8+8=

Method 1

What you need to understand about this logical question is that it is a carefully defined pattern..You will notice that from (1) 4+4=20 and (2) 5+5=30; the difference between the answers of (1) and (2) is 10 [i.e. 30-20=10]..

This means that you always add 10 to an answer to obtain the next answer. However whenever you add the 10 to an answer you will notice you have to also add these even numbers to your result to obtain the next answer..The even numbers are EVEN NUMBERS= 2;4;6;8;10..

Therefore adding 10 to 20[this 20 is the answer to (1)] gives 30[this 30 is the answer to (2)]..

Now adding 10 to this 30 gives, 10+30=40..now add the first EVEN NUMBER listed above i.e. 2 which gives 40+2=42 [this 42 is answer to (3)]

..Then adding 10 to 42 gives 10+42=52…but 52 isn’t the answer to the (4)..Add the next EVEN NUMBER which is 4 i.e. 52+4=56..

Now we can confidently say that to obtain the next sequence, which is 8+8=?? We get the answer to 7+7=56..

10+56=66…adding the next EVEN NUMBER is 66+6=72 which is answer to 8+8=72;

To reproduce the next sequence, 9+9=?? We proceed as follows;

10+72=82; now add 8 to the result which gives 82+8=90..

Therefore 9+9=90

Duad erat demonstradum