Mumsnet users have been left stumped by this maths question aimed at primary school age children - but can you solve it? 'The first light shines for 3 seconds then it is off for three seconds. The second light shines for 4 seconds then it is off for 4 seconds. The third light shines for 5 seconds then it is off for 5 seconds. The question left many parents baffled as they couldn't even begin to work out what the answer was.

Source: Daily Mail May 13, 2018 14:03 UTC