The Hard Grade 9 Questions Thread 2019

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OP

Original post by IsMo987

Help please can someone out line the method I would need and the equation for the radius and angle

First you need to find the radius of the sector in the diagram. Please post what you’ve tried.

Original post by Notnek

First you need to find the radius of the sector in the diagram. Please post what you’ve tried. 30EEA10C-9120-4F55-8ED7-3FA3941647CC.jpg.jpeg

30EEA10C-9120-4F55-8ED7-3FA3941647CC.jpg.jpeg

E0D5D02D-6C39-4397-80E2-CF173206F089.jpg.jpeg20.3KB

Original post by IsMo987

Help please can someone out line the method I would need and the equation for the radius and angle

i cud if it was rotated

Original post by salimyasin10

i cud if it was rotated

What do you mean

OP

Original post by IsMo987

Original post by Notnek

First you need to find the radius of the sector in the diagram. Please post what you’ve tried. 30EEA10C-9120-4F55-8ED7-3FA3941647CC.jpg.jpeg

30EEA10C-9120-4F55-8ED7-3FA3941647CC.jpg.jpeg

Sorry, ignore my last post - finding the radius is not necessary.

Since the formula is

A=\frac{\theta}{ 360 } \pi r^2

, if the radius is fixed then

A

is proportional to

\theta

. So you can use basic ratio/proportion methods to find the area here. Does that make sense?

Original post by Notnek

Sorry, ignore my last post - finding the radius is not necessary.

Since the formula is

Unparseable latex formula:

A=\frac{\theta}{360) \pi r^2

, if the radius is fixed then

A

is proportional to

\theta

. So you can use basic ratio/proportion methods to find the area here. Does that make sense?

Noooo😭😭😭

i cant see the pic properly

Original post by IsMo987

What do you mean

OP

Original post by IsMo987

Noooo😭😭😭

The area is proportional to the angle. So if the angle doubles then the area will double (assuming the radius remains the same).

So you can ignore the fact that this is a sector and just use basic ratio. Still unsure?

Original post by Notnek

The area is proportional to the angle. So if the angle doubles then the area will double (assuming the radius remains the same).

So you can ignore the fact that this is a sector and just use basic ratio. Still unsure?

How do you know it’s proportional tho sorry for being annoying

OP

Original post by IsMo987

How do you know it’s proportional tho sorry for being annoying

Because the formula is

A=\frac{\theta}{360} \times \pi r^2

So if the radius remains the same (i.e. it's a constant) then the whole right-hand-side is just some constant multiplied by

\theta

:

A = k\theta

where

k

is some constant. So A must be proportional to

\theta

.

Original post by salimyasin10

i cant see the pic properly

I

11D0E781-18B8-4097-A3EB-FD318EEF68D4.jpg.jpeg

OP

@IsMo987 if you don't like this method (most GCSE students wouldn't) then you can just find the radius and go from there but it's a much longer method. But if you're targeting an 8/9 then you should be comfortable with this kind of proportionality argument.

OP

If you're targeting grade 8/9 and need a circle theorems challenge then have a go at this :smile:

:smile:

Definitely print it out first.

yh

Original post by Notnek

If you're targeting grade 8/9 and need a circle theorems challenge then have a go at this :smile:

:smile:

Definitely print it out first.

Do you have any more hard non calculator questions especially for ratio and proportion if you don’t could you please make some

x^2+157x+12=0 Solve with the quadratic formula to find x.

thanks, i got 42.5, is that right?

Original post by IsMo987

I

11D0E781-18B8-4097-A3EB-FD318EEF68D4.jpg.jpeg

Original post by salimyasin10

thanks, i got 42.5, is that right?

Yh could you send me your working

Original post by salimyasin10

thanks, i got 42.5, is that right?

8A2CF629-ADB0-4B43-AB9D-301D31288CB2.jpg.jpeg

what about this one

i cant see it clearly but dd i get the first one right, also did u? coz it was long but quite straightfoward

Original post by IsMo987

8A2CF629-ADB0-4B43-AB9D-301D31288CB2.jpg.jpeg

what about this one

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