Maths Question Help

II 2FAST2C II

Please if anyone can help me within an hour would be great
12 Block layers can build a wall in 15 days
(i)How long would it take 20 block layers working at the same rate
(ii) How many block layers would be needed to build wall in 10 days

TheBody

II 2FAST2C II wrote: »

Please if anyone can help me within an hour would be great
12 Block layers can build a wall in 15 days
(i)How long would it take 20 block layers working at the same rate
(ii) How many block layers would be needed to build wall in 10 days

There are a few ways to do this. If it takes 12 block layers 15 days, how long would it take 1 block layer?

II 2FAST2C II

TheBody wrote: »

There are a few ways to do this. If it takes 12 block layers 15 days, how long would it take 1 block layer?

Hi than you very much for taking interest i did 15/12 and i got 1.25

II 2FAST2C II

And then i 1.25*20 and i got 25 while in the back of the book says 9

If it takes 12 block layers 15 days, then in would take 1 block layer longer, ie 12 x 15 days

TheBody

II 2FAST2C II wrote: »

Hi than you very much for taking interest i did 15/12 and i got 1.25

Think about it again. You are on the correct track. If it takes 12 block layers 15 days then surely it'll take 1 block layer 12 times longer. In other words it would take 1 block layer [latex]12 \times 15=180[/latex]days. So if it takes 1 block layer 180 days, how long will it take 20 block layers? (will it be more or less than 180 days?)

II 2FAST2C II

Alright thanks and then you / by 9 thanks guys

TheBody

II 2FAST2C II wrote: »

Alright thanks and then you / by 9 thanks guys

That's the idea. Well done. In general I advise you to think about what you are doing and not just accept any old number you get after doing a calculation. If you think about your first attempt, you probably would have know that if 12 block layers take 15 days then surely 1 block layer couldn't have done it in 1.25 days.

II 2FAST2C II

Now what would be part (II)

NoQuarter

Its a ratio problem.

12 is to 15 as what is to 10?

12:15
=
??:10

TheBody

II 2FAST2C II wrote: »

Now what would be part (II)

Same idea. If it takes 12 block layers 15 days, how many block layers would it take to get it done in 1 day? (Think about it....would it be more or less than 12?)

NoQuarter

TheBody wrote: »

Same idea. If it takes 12 block layers 15 days, how many block layers would it take to get it done in 1 day? (Think about it....would it be more or less than 12?)

eh? Have you mixed up the quesions?

II 2FAST2C II

TheBody wrote: »

Same idea. If it takes 12 block layers 15 days, how many block layers would it take to get it done in 1 day? (Think about it....would it be more or less than 12?)

Well to be honest with you i got this one by luck just right now i did 180/10 but to my understanding i do not know how i got it i just did it by luck form the previous i answer tried to divide by 10

TheBody

NoQuarter wrote: »

eh? Have you mixed up the quesions?

No.

NoQuarter

II 2FAST2C II wrote: »

Well to be honest with you i got this one by luck just right now i did 180/10 but to my understanding i do not know how i got it i just did it by luck form the previous i answer tried to divide by 10

Stupidity edit :pac:

NoQuarter

TheBody wrote: »

No.

Sorry, I get what way you were coming at it now.

II 2FAST2C II

NoQuarter wrote: »

What you do is break the ration into its lowest fraction so

12:15 turns into 4/5 Then you find 4 5ths of 10 and you get your answer. 8 block layers to build a wall in 10 days.

Thats wrong answer at the back of book it says 18

TheBody

NoQuarter wrote: »

What you do is break the ration into its lowest fraction so

12:15 turns into 4/5 Then you find 4 5ths of 10 and you get your answer. 8 block layers to build a wall in 10 days.

This is incorrect. How could it take less people to do it in less time!!

NoQuarter

II 2FAST2C II wrote: »

Thats wrong answer at the back of book it says 18

I've made a right mess of that haha!

18 is the right answer.
If it takes 1 block layer 180 days,
you need to get this down to 10 days
180/10=18

TheBody

II 2FAST2C II wrote: »

Thats wrong answer at the back of book it says 18

18 is correct.

12 block layers take 15 days. So it would take 12 X 15=180 to get it done in 1 day. Therefore it would take 18 block layers to get it done in 10 days.

II 2FAST2C II

One last question if you do not mind its just that our teacher never thought us how to do this one
The perimeter of a rectangle is 200cm
If length:Breadth=7:3, find the area of the rectangle

II 2FAST2C II

II 2FAST2C II wrote: »

One last question if you do not mind its just that our teacher never thought us how to do this one
The perimeter of a rectangle is 200cm
If length:Breadth=7:3, find the area of the rectangle

perimeter is 2(length + breath)
let x stand for the distance the ratio stand for
2(7x + 3x) = 200
20x = 200
x =10
length is 7x ie 7(10 centimetres) = 70cm
breath is 3x
the rest should be more straight forward

TheBody

II 2FAST2C II wrote: »

One last question if you do not mind its just that our teacher never thought us how to do this one
The perimeter of a rectangle is 200cm
If length:Breadth=7:3, find the area of the rectangle

This isn't too bad. So you need 7 parts off 200 cm along the two lengths and 3 parts along the two breadths. In total you need 10 parts. So you divide 200cm by 10 to give you 20cm. They you want 7X20=140cm along the two lengths and 3X20 60cm along the two breadths. Therefore the length of one side is 70cm and breadth of one side is 30cm. The area is then just [latex]70\times 30=210cm^{2}[/latex].

II 2FAST2C II

''Therefore the length of one side is 70cm and breadth of one side is 30cm.''
Did you just half it
60=30 and 140=70

TheBody

II 2FAST2C II wrote: »

''Therefore the length of one side is 70cm and breadth of one side is 30cm.''
Did you just half it
60=30 and 140=70

Yes.

II 2FAST2C II

I really hope i get a B in Junior Cert even though the way i am going i doubt it but if i get an B i will be over the moon
Thanks all who could take their special time out and help me i hope i was not bother to you

TheBody

II 2FAST2C II wrote: »

I really hope i get a B in Junior Cert even though the way i am going i doubt it but if i get an B i will be over the moon
Thanks all who could take their special time out and help me i hope i was not bother to you

Good luck. Keep your head down, work hard and you will do great. Don't forget there is a maths forum too:

http://www.boards.ie/vbulletin/forumdisplay.php?f=380

I'm usually lurking over there.

MJ434

I need help with this one :

If X = p+q/p-q ,express p in terms of q and x

zom

TheBody wrote: »

Think about it again. You are on the correct track. If it takes 12 block layers 15 days then surely it'll take 1 block layer 12 times longer. In other words it would take 1 block layer [latex]12 \times 15=180[/latex]days. So if it takes 1 block layer 180 days, how long will it take 20 block layers? (will it be more or less than 180 days?)

Ho how many block layers we need to build a house in 360 days??

TheBody

MJ434 wrote: »

I need help with this one :

If X = p+q/p-q ,express p in terms of q and x

Hi there.

[latex]x=\frac{p+q}{p-q}[/latex]

Multiplying both side by [latex]x=p-q[/latex] to get:

[latex]x(p-q)= p+q[/latex]

Multiply out the left hand side to get:

[latex]xp-xq= p+q[/latex]

Subtract [latex]p[/latex] from both sides:

[latex]xp-xq-p=q[/latex]

Add [latex]xq[/latex] to both sides:

[latex]xp-p=q+xq[/latex]

Factorise p out of the left hand side:

[latex]p(x-1)=q+xq[/latex]

Divide both sides by [latex](x-1)[/latex] to get:

[latex]p=\frac{q+xq}{(x-1)}[/latex]

MJ434

Hi,
Thanks a mill for that...

U wouldn't be able to help me with this one would u? :P

Solve the equation:

1/x-1 + 4/x = 3

Thanks!

Sir Ophiuchus

Multiply all the elements in that equation by all the bottom lines. They should cancel out so everything ends up "above the line" and you have no fractions. Then you'll just have a regular equation in x, which you can shuffle around to solve for x.

II 2FAST2C II

Sir Ophiuchus wrote: »

Multiply all the elements in that equation by all the bottom lines. They should cancel out so everything ends up "above the line" and you have no fractions. Then you'll just have a regular equation in x, which you can shuffle around to solve for x.

do you multiply everything by 3 also

TheBody

II 2FAST2C II wrote: »

do you multiply everything by 3 also

No need to. Just multiply everything by x(x-1)

Sir Ophiuchus

TheBody wrote: »

No need to. Just multiply everything by x(x-1)

What they said.

Hint: 3 isn't on the bottom line. 3 is the same as 3/1.

MJ434

Can some do this one:
Simplify (2x-z)(6x+3z)-(6a-3z)(2a+z) and factorise full the simplified expression.
Thanks

MJ434

TheBody wrote: »

Can some do this one: Simplify (2x-z)(6x+3z)-(6a-3z)(2a+z) and factorise full the simplified expression. Thanks