Year 7 maths problem
Moderators: Section Moderators, Forum Moderators
-
- Posts: 138
- Joined: Sat Apr 17, 2010 3:53 pm
Year 7 maths problem
Question:
How many panes of glass 30cmx20cm can be cut from a sheet which is 1 metre square?
DD worked out answer to be 15.
Answer corrected by teacher to 16. I don't understand correction. I get 15 too as surely they need to be whole sheets?
What am I missing?
How many panes of glass 30cmx20cm can be cut from a sheet which is 1 metre square?
DD worked out answer to be 15.
Answer corrected by teacher to 16. I don't understand correction. I get 15 too as surely they need to be whole sheets?
What am I missing?
-
- Posts: 888
- Joined: Wed Aug 01, 2007 12:19 pm
Re: Year 7 maths problem
Your dd is right! Teacher perhaps has just done 10000/600? If it is definitely 1 metre square, and not 1 square metre, to be arranged in whatever the optimum rectangle would be.
Your dd should just ask the teacher to draw it for her
Your dd should just ask the teacher to draw it for her
-
- Posts: 12906
- Joined: Fri Sep 15, 2006 9:51 am
- Location: The Seaside
Re: Year 7 maths problem
hmm is it one of these ones where you can get 2*30cm + 2*20cm on one side ?
so one quarter of the sheet = 50cm by 50cm and you could get 4 pieces arranged with a 20 and a 30 on each side in a pattern like this picture : (well each quarter of your sheet would be one of these small squares on this) and there would be a little bit in the middle left over
so one quarter of the sheet = 50cm by 50cm and you could get 4 pieces arranged with a 20 and a 30 on each side in a pattern like this picture : (well each quarter of your sheet would be one of these small squares on this) and there would be a little bit in the middle left over
-
- Posts: 138
- Joined: Sat Apr 17, 2010 3:53 pm
Re: Year 7 maths problem
Thanks hermanmunster!
The teacher's explanation of 10000/600 was a little incorrect imho. However 16 is indeed right!
The teacher's explanation of 10000/600 was a little incorrect imho. However 16 is indeed right!
-
- Posts: 452
- Joined: Mon Aug 12, 2013 10:13 am
Re: Year 7 maths problem
15 panes, unless the teacher wants to cut the 16th one into smaller pieces and fit in the remainder 10x100 cm area.
Not surprised by the teaching standard, I guess parents are more intelligent these days. God help the class
Not surprised by the teaching standard, I guess parents are more intelligent these days. God help the class
Re: Year 7 maths problem
Having no luck trying to draw this out in Word, but try:
4 columns - two of one pane across, 5 down (landscape) and two of one pane across, three down (portrait). There will be a 10cm x 40cm piece of glass remaining at the base of the third and fourth columns.
16 panes total.
4 columns - two of one pane across, 5 down (landscape) and two of one pane across, three down (portrait). There will be a 10cm x 40cm piece of glass remaining at the base of the third and fourth columns.
16 panes total.
Outside of a dog, a book is a man's best friend. Inside of a dog it's too dark to read.Groucho Marx
Re: Year 7 maths problem
I've drawn it out and got 16 too. Drawn differently to Herman.
Hopefully this helps. Letters grouped together signify a pane of glass.
oooxxxooxx
oooxxxooxx
xxxcccooxx
xxxcccxxoo
ccceeexxoo
ccceeexxoo
eeeaaaooxx
eeeaaaooxx
ccceeeooxx
ccceee----
Hopefully this helps. Letters grouped together signify a pane of glass.
oooxxxooxx
oooxxxooxx
xxxcccooxx
xxxcccxxoo
ccceeexxoo
ccceeexxoo
eeeaaaooxx
eeeaaaooxx
ccceeeooxx
ccceee----
Re: Year 7 maths problem
The topic is tessellations, so it involves a bit of trial and error, and thinking rather than straightforward calculating.
Re: Year 7 maths problem
Why is 10000/600 wrong? That's how I would have worked it out?
Area 100x100= 10000
Area of tile 20x30=600
So 10000/600 = 16.67. So 16 complete tiles?
Area 100x100= 10000
Area of tile 20x30=600
So 10000/600 = 16.67. So 16 complete tiles?
Re: Year 7 maths problem
That method assumes the shapes fit in with nothing to spare.
These questions always need you to look at whether dimensions fit; it is not really about area.
These questions always need you to look at whether dimensions fit; it is not really about area.