One in ten children do not realise they live on planet Earth, while one in 10 do not know a triangle has three sides, new research has revealed.
And while youngsters can recognise popular children's television personalities and celebrities, four in 10 could not identify an avocado, a recent poll has shown.
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The newly-released research shows gaps in the knowledge of children aged six to 10, with only nine in 10 knowing a square has four sides.
According to the poll of 500 children, nearly nine in 10 (87%) recognised a picture of CBeebies personality Mr Tumble, with 85% recognising David Beckham; 80% identifying Simon Cowell; 72% recognising Prince William; and 70% being able to name Prime Minister David Cameron from a picture.
But when shown a picture of an avocado, just 62% could say what it was, with nearly a quarter (24%) saying they did not know, while others identified it as various other items of fruit.
As research this week revealed that five portions of fruit and vegetables may not be enough after all, more than half (53%) said they had not tasted avocado; while more than two-thirds (68%) had not tried kale.
Some 15% polled said they had not tasted cabbage, with 9% having not tried broccoli, and 11% (one in 10) saying they had not tasted onions.
The research, released today by Alton Towers Resort and carried out by One Poll, polled 500 children aged six to 10.
According to the findings, nine in 10 children thought a square had four sides, one in 10 getting the number of sides wrong.
And nine out of 10 knew a triangle had three sides - with 4% thinking it only had two.
One in 10 children did not realise they lived on planet Earth, with 88% saying it was where they were from - and some believing they lived on Saturn or Mars.
And while half of the children correctly identified the theme song to ZingZillas (51%), a popular show on BBC pre-school channel CBeebies, only slightly more than that - 64% - recognised the National Anthem.
The research comes as CBeebies Land at Alton Towers Resort prepares to open its gates for the first time on May 24.
Mat Way, BBC Worldwide's Commercial Director, Live Events, said: "We've found that children learn best when they're interacting and CBeebies Land will continue to encourage learning through play.
"By giving children the chance to discover things for themselves, we can help improve their development while they're having fun."
Katherine Duckworth, from Alton Towers Resort, added: "We're really excited about the launch of CBeebies Land and can't wait to see the children having fun with the different characters.
"While this poll shows that some older children have some gaps in their general knowledge, CBeebies Land is a place where children can come and enjoy themselves but also learn a little more about the world around them."