sunnyday Posted July 12, 2009 Share Posted July 12, 2009 So.....as if I haven't got enough to do......... My grandson will sit his 11+ third week of September (yes, they still do this in sunny Kent).......I have said that I will help him through the summer holiday To this end no.1 son delivered 4 books this morning ... I have spent much of the day looking through them to make sure 'nana' knows whats what before we start So.... English, Verbal Reasoning, Non-Verbal Reasoning - no probs. - child's play!!! Maths - aargh.......I knew this would be where I would fall down So.....try this on for size...... The area of a rectangle is 48 cm2. What could be the perimeter of the rectangle? 12cm 14cm 18cm 28cm 30cm OK....the answer is 28cm....I know that because it's on the answer page! Can anyone explain how you get there? Sunnyday Quote Link to comment Share on other sites More sharing options...
HappyMaz Posted July 12, 2009 Share Posted July 12, 2009 Can anyone explain how you get there? Of course - its plain for all to see. You looked at the answer page. Maz Quote Link to comment Share on other sites More sharing options...
sunnyday Posted July 12, 2009 Author Share Posted July 12, 2009 Of course - its plain for all to see. You looked at the answer page. Maz Funny - but not helpful!.....I was so excited when I saw you had replied......I thought great Maz knows how to do it Quote Link to comment Share on other sites More sharing options...
mundia Posted July 12, 2009 Share Posted July 12, 2009 aha here's one I can answer... yes but will I? Quote Link to comment Share on other sites More sharing options...
HappyMaz Posted July 12, 2009 Share Posted July 12, 2009 aha here's one I can answer... yes but will I? Don't tell me mundia - does your face look bothered? Quote Link to comment Share on other sites More sharing options...
Guest Posted July 12, 2009 Share Posted July 12, 2009 (edited) hmm now this is a tricky one to explain...i will try my best although i am no maths person. in my head i picture 48 cubes (because that is what the area is) which need to be made into a rectangle so this would be 4 rows of 12. if i have lost you by this point i do apologize as i said very hard to explain my thoughts. the perimeter is then how many cubes make up the four edges.... 12 along the top and bottom and then each side has an extra two which equals 28!!!! hope this helps a bit, if not i am sure some one else will come along who has a maths brain xx Edited July 12, 2009 by samfrostie Quote Link to comment Share on other sites More sharing options...
sunnyday Posted July 12, 2009 Author Share Posted July 12, 2009 aha here's one I can answer... yes but will I? Na na na na ....Sam already told me Quote Link to comment Share on other sites More sharing options...
Guest Posted July 12, 2009 Share Posted July 12, 2009 The square area is the length X the width, so for 48cm sq two sides would be 6cm and two sides would be 8cm, (8 X 6 = 48) so the perimiter (the cummulative length around the rectangle) is 6 + 6 + 8 + 8 = 28cm . This is just an example because: example 2 - the sides could be 12cm and 4cm (12 x 4 = 48) = 12+4+12+4= perimiter of 32 or example 3 - the sides could be 48cm and 1cm (48 x 1) = 48+1+48+1 = perimiter of 98 or any combination of length x width to equal 48. This is why the question says what COULD the perimitar be. So even if the shape of the rectangle changes, ie the perimiter increases or decreases in total length, the 'area' can remain the same at 48cm square ooh just noticed that you had multiple choice answers with only one perimiter length that could fit 'around' the area, so although not wrong ignore my examples 2 & 3. Peggy thanks to hubby who explained it to me. Quote Link to comment Share on other sites More sharing options...
Guest Posted July 12, 2009 Share Posted July 12, 2009 haha i did but question is does it make sense Quote Link to comment Share on other sites More sharing options...
sunnyday Posted July 12, 2009 Author Share Posted July 12, 2009 hmm now this is a tricky one to explain...i will try my best although i am no maths person. in my head i picture 48 cubes (because that is what the area is) which need to be made into a rectangle so this would be 4 rows of 12. if i have lost you by this point i do apologize as i said very hard to explain my thoughts. the perimeter is then how many cubes make up the four edges.... 12 along the top and bottom and then each side has an extra two which equals 28!!!! hope this helps a bit, if not i am sure some one else will coem along who has a maths brain xx Brilliant! - thank you, thank you, thank you Anyone up for another one? Quote Link to comment Share on other sites More sharing options...
Guest Posted July 12, 2009 Share Posted July 12, 2009 go on will give it a go Quote Link to comment Share on other sites More sharing options...
sunnyday Posted July 12, 2009 Author Share Posted July 12, 2009 (edited) thanks to hubby who explained it to me. Would he like to do some maths tutoring over the summer break?!!! Edited July 12, 2009 by sunnyday Quote Link to comment Share on other sites More sharing options...
mundia Posted July 12, 2009 Share Posted July 12, 2009 Well tried sam, but your rectangle has a perimeter of 32 because you add the 12, 12, 4, and 4. The trick to this question is to realise that there are several correct answers but only ONE of the given answers is correct. The area is 48. We need to find two number which when multiplied would make 48: Sam suggested 4 x12. try 6x8. Now if your rectangle is 6 x8, then its perimeter (round the outside edge) is 8+8+6+6 which is 28. Now in true mundia style, if you follow my logic, what is the possible perimeter of a rectangle that is 36cm2? Quote Link to comment Share on other sites More sharing options...
sunnyday Posted July 12, 2009 Author Share Posted July 12, 2009 OK......... Jamal will be a years old in four years time> How old was he eight years ago in terms of a? Quote Link to comment Share on other sites More sharing options...
Guest Posted July 12, 2009 Share Posted July 12, 2009 (edited) hmmm i still mine as being right but im no expert Edited July 12, 2009 by samfrostie Quote Link to comment Share on other sites More sharing options...
Marion Posted July 12, 2009 Share Posted July 12, 2009 Now in true mundia style, if you follow my logic, what is the possible perimeter of a rectangle that is 36cm2? 30cm 74cm 40cm 24cm 26cm I think Quote Link to comment Share on other sites More sharing options...
Panders Posted July 12, 2009 Share Posted July 12, 2009 Surely by counting 12,12, 4, 4, you are counting the "corners" of the rectangle twice Mundia Quote Link to comment Share on other sites More sharing options...
Marion Posted July 12, 2009 Share Posted July 12, 2009 (edited) hmmm i still mine as being right (12x4) because i wuld be adding 12, 12, 2 and 2 who knows im no expert sorry sam I agree with mundia your rectangle is 12x4 =48 not 12 x2 panders you have to measure the outer edge Edited July 12, 2009 by Marion Quote Link to comment Share on other sites More sharing options...
Panders Posted July 12, 2009 Share Posted July 12, 2009 Sunnyday, you need the Collins Maths Dictionary - that's what got my lot through their maths 11+. It gives all types of examples on all kinds of maths. Quote Link to comment Share on other sites More sharing options...
Guest Posted July 12, 2009 Share Posted July 12, 2009 panders you have my thinking Quote Link to comment Share on other sites More sharing options...
mundia Posted July 12, 2009 Share Posted July 12, 2009 Sadly Sam, I can see where you are going but if you imagine the cubes you laid out in 4 rows of 12, you still have to walk around all of the edges to make the perimeter. So the cubes in your corners you have to walk around 2 edges of, not just one, hence needing to add 4 and 4 not 2 and 2. Quote Link to comment Share on other sites More sharing options...
sunnyday Posted July 12, 2009 Author Share Posted July 12, 2009 Sunnyday, you need the Collins Maths Dictionary - that's what got my lot through their maths 11+. It gives all types of examples on all kinds of maths. Right........off to Amazon! Anyone know how old Jamal was eight years ago? Anyone care? Quote Link to comment Share on other sites More sharing options...
Guest Posted July 12, 2009 Share Posted July 12, 2009 (edited) ok convinced Edited July 12, 2009 by samfrostie Quote Link to comment Share on other sites More sharing options...
Marion Posted July 12, 2009 Share Posted July 12, 2009 Try here Quote Link to comment Share on other sites More sharing options...
Guest Posted July 12, 2009 Share Posted July 12, 2009 OK......... Jamal will be a years old in four years time> How old was he eight years ago in terms of a? guess, hubby is now out the room if 'in terms of a' means 'now' I guess; a + 4 = b a- 8 = b - 12 or i 'in terms of a' is in 4 yrs time? a + 4 - 8 = ???? stumped Quote Link to comment Share on other sites More sharing options...
mundia Posted July 12, 2009 Share Posted July 12, 2009 sam, sorry I cant produce a picture for you, I dont have that level of skill. If you were in my class, Id show you in order to convince you, I wouldnt like you to just accept it without understanding! Well done marion, for the answers to my other challenge which got lost in the replies somewhere. jamal's age is I believe a+12. Quote Link to comment Share on other sites More sharing options...
sunnyday Posted July 12, 2009 Author Share Posted July 12, 2009 Right........off to Amazon! Anyone know how old Jamal was eight years ago? Anyone care? Blimey....that 'buy now with one click' is a dangerous thing!!! Quote Link to comment Share on other sites More sharing options...
sunnyday Posted July 12, 2009 Author Share Posted July 12, 2009 jamal's age is I believe a+12. The gold star goes to Mundia! Quote Link to comment Share on other sites More sharing options...
mundia Posted July 12, 2009 Share Posted July 12, 2009 And if I had read the question properly Jamal was in fact a-12 not a+12 as I said! Quote Link to comment Share on other sites More sharing options...
Guest Posted July 12, 2009 Share Posted July 12, 2009 i can see what your saying Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.