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Original poster

A maths reasoning question.

43 replies

WelshMoth · 15/04/2019 20:02

I'm scratching my head as to how to tackle this:

See pic.

Consider the black and white shape in the pic. Which statement is correct?

A) the perimeter of the black shape is the largest

B) the perimeter of the white shape is the largest

C) the perimeter of both is equal.

Help!

OP posts:
Original poster
WelshMoth · 15/04/2019 20:03

Oops. Pic now attached.

A maths reasoning question.
OP posts:
dementedpixie · 15/04/2019 20:03

No pic

QueenofLouisiana · 15/04/2019 20:03

I can’t see a pic!

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Original poster
WelshMoth · 15/04/2019 20:04

Is it there now?!

This is driving me nuts.

OP posts:
dementedpixie · 15/04/2019 20:06

It's on the app

Soontobe60 · 15/04/2019 20:06

Nope! No picture

Original poster
WelshMoth · 15/04/2019 20:08

Nooooooooo!!!!
I can see the pic on my phone (app)!! What's happened?!

OP posts:
JustPurple · 15/04/2019 20:09

I'd say equal.
Each side of the black shape is also the side of a white shape. There are 4 of them for both shapes.

Lwmommy · 15/04/2019 20:10

They're equal. Each 'side' is the same length, there's 16 on each shape

1sttimeDD · 15/04/2019 20:10

Surely the perimeter is equal as the black shape is the opposite of the white shape as it is a tesselation. Each shape has the same number of sides, which are all equal in length.

Original poster
WelshMoth · 15/04/2019 20:13

Thanks. Off to google tessalation

OP posts:
PurpleDaisies · 15/04/2019 20:14

I feel something in my life is missing because I can’t see the picture..

dementedpixie · 15/04/2019 20:15

If you go on the app it's there

Original poster
WelshMoth · 15/04/2019 20:16

Sorry PurpleGrin

For the record, I'm confused even WITH the picture there.

OP posts:
dementedpixie · 15/04/2019 20:17

Here

A maths reasoning question.
Original poster
WelshMoth · 15/04/2019 20:17

Still don't get it.

OP posts:
PotteryLady · 15/04/2019 20:27

Equal

PotteryLady · 15/04/2019 20:29

Each shape has 16 equal sides - so perimeter of both shapes equal

PurpleDaisies · 15/04/2019 20:30

Thanks demented. That’s made me happier than it really should have!

Yes, the perimeters are equal. The white shape is effectively formed by the edges of the black shapes.

Original poster
WelshMoth · 15/04/2019 21:50

The area looks like it should be equal, but the actual perimeter looks like the black should be bigger.

This is for 13 yr olds!!!

OP posts:
PurpleDaisies · 15/04/2019 22:08

The area definitely isn’t equal. You’ve got a basic square to start both shapes. The black has triangles added on increasing the area. The white one has triangles cut out which decreases the area.

spugzbunny · 15/04/2019 22:15

@PurpleDaisies that's correct for area.

For perimeter, the removed/added triangles mean the perimeter is the same on both.

If you aren't sure OP, draw it and measure with a ruler

spugzbunny · 15/04/2019 22:15

You only need to draw and measure one of each square

xyzandabc · 15/04/2019 22:20

They are equal.

One side of the white shape is the same length as the side of the black shape. All 4 sides are the same.

If the perimeters were different lengths, they woudlnt' slot perfectly together. The shapes would either overlap or have a space between them.

mineofuselessinformation · 15/04/2019 22:27

8 horizontals and 8 diagonals will on each, so they are equal.

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