Tricky brainteaser originally branded 'easy' leaves viewers reeling - see if you can do it

One maths-based can be solved by most people, so can you work it out?

Around 90 percent of people can pass according to the Hindustan Times. All you have to do is the last sum in the list, a simple 10+10. But the answer is not 20 and using the answers in sums previously listed in the clue, you have to work out the missing part of the calculation to find the right answer.

So are you part of the 90 percent that got this numbers riddle right? Find the image and the answer below.

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In this , the first three sums all have an answer that is 18 less than it should be. Take 11+11, for example. That should add up to 22, but instead the answer is listed as just four. This is the same for 13+13, where the answer is given as eight instead of 26 and for 17+17, where the answer is given as 16 instead of 34.

For the 10+10, you must therefore apply the same rule. Simply subtract 18 from the original answer of 20 and you have your answer: the sum should equal two.

Brainteasers aren't just a good way to pass the time as the days become darker and colder, they are also good for your cognitive health. Completing challenging , brainteasers and optical illusions may help improve your cognitive function, boost productiveness and memory. Aaron Seitz, PhD., professor of psychology and director of the Brain Game Centre at the University of California in Riverside told Real Simple: "Studies show that staying mentally fit is important for long-term cognitive health, but the difficulty is figuring out exactly how to do it.”

Nicole M. Avena, PhD, assistant professor of neuroscience at the Mount Sinai School of Medicine in New York City and visiting professor of health psychology at Princeton University said: “While some studies show that brain training games are not effective, the recollection and work that the brain does during these games keeps your mind fresh and alert… Brain functions that you practise during these games—and the repetition of them—can help improve response time and sharpness.”

If you're ready for your next quest, there are plenty more brainteasers you can complete. Whether they test your memory skills, quick-thinking or powers of observation, there's no greater thrill than beating the clock. Why not attempt to Or, if you're up for something a little more tricky, you can try to Or, see whether you have a 'highly intelligent mind' by .