Maths Help Needed

pinkymary

Doesn't anyone know how to do the 2014 sec sample paper 1 question 7 , really stuck :rolleyes:

Moody_mona

Level?

Peregrine

Which level?

pinkymary

oh sorry higher

Peregrine

Ah the jelly bean box question..


Is it a specific part you need help with or just all of it?

Can you express the dimensions in terms of h? (part a)

pinkymary

yes that question , need help with everything , thanks

Peregrine

In part a, you have to write down the dimensions of the box in terms of h.

For width, it would be 22 cm take away the length of the two flaps which are both 1cm each and the two hs

For length, take away the 1cm of the flap and the 2 hs of the sides from 31cm. But that gives you with the sum of the length of the bottom and top and they're both equal so you can divide it by two to get the expression for either one.

For part b, it's only asking you to do the volume of the box, in terms of h. You have the three sides, you should be able to do that.

Part c, for a square base, the length has to be equal to the width. Do that and solve for h. Once you have h, use it to prove that the volume it gives is the volume of the box given in the question. You should have an expression for volume of the box from part 3 where you can sub in h.

Part d, this one is a little bit more complicated. Let the expression for the volume of the box be equal to 500. Now, this is a cubic expression and you know one of the roots, from part c, it's asking you to find another root. If the answer you got from c was 5, the root, h-5 is a factor. Do you know how to divide cubic equations? Divide it by h-5 and you will get a quadratic, factorise that and get the other 2 roots, only one of them is valid.

I'll do part e in a second.

pinkymary

Thank you so much

Peregrine

Okay, part e.

If they increase the volume by 10%, the volume will be 550cm cubed. If you look at the graph, the only value of h that gives a volume of 550 is just over 17cm.

But since the length and width remains the same, 15-h and 20-2h. h=17 point whatever isn't valid because the dimensions of the base would be negative..and you can't have a negative distance.

pinkymary wrote: »

Thank you so much

You're welcome.

IIRC, studentxpress.ie has solutions to past papers and the sample paper. You might find them useful.

moss1234

Does anyone know how to do question 9 b (ii) and (iii) and also c (i) and (ii) on the sec sample paper 1 2014, thanks

Ompala

moss1234 wrote: »

Does anyone know how to do question 9 b (ii) and (iii) and also c (i) and (ii) on the sec sample paper 1 2014, thanks

I might be wrong about c(ii), you might be better off asking in the maths forum about it. I think the others are correct though.

moss1234

Ompala wrote: »

I might be wrong about c(ii), you might be better off asking in the maths forum about it. I think the others are correct though.

Thanks a million