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Anyone Good At Maths?


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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 :o

 

So.... English, Verbal Reasoning, Non-Verbal Reasoning - no probs. - child's play!!!

 

Maths - aargh.......I knew this would be where I would fall down xD

 

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

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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 by samfrostie
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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. :(:o

 

 

 

Peggy

 

thanks to hubby who explained it to me. xD

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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 :o

 

Anyone up for another one?

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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?

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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.

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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

 

:oxD

 

or i 'in terms of a' is in 4 yrs time?

 

a + 4 - 8 = ????

 

stumped

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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.

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