Mathematics (HELP) 3

Steph is solving a problem. Cube A has a surface area of 150 cm2 Cube B has sides half the length of cube A

What is the volume of cube B?

To solve this problem, Steph decides to:
- halve the surface area
-calculate the square root of the answer then divide by 6
- then cube this answer to work out the volume.
Evaluate Steph’s method.

[2 marks]

Reply 1

thekidwhogames

18

I won't give the answer but some hints.

If cube A has surface area 150, then 6x^2=150 --> x^2 = 25. This mean each side length is 5 then you can...?

Also you probably made a mistake copying the question in the second bullet point -these shouldn't be together in the same point.

Reply 2

username2857056

OP

11

Original post by thekidwhogames

I won't give the answer but some hints.

If cube A has surface area 150, then 6x^2=150 --> x^2 = 25. This mean each side length is 5 then you can...?

Also you probably made a mistake copying the question in the second bullet point -these shouldn't be together in the same point.

I actually have no idea whats going on :frown:

and its 2 marks as well- don't understand.

Reply 3

Baza2002

19

Original post by GCSE_18

Steph is solving a problem. Cube A has a surface area of 150 cm2 Cube B has sides half the length of cube A

What is the volume of cube B?

To solve this problem, Steph decides to:
- halve the surface area
-calculate the square root of the answer then divide by 6
- then cube this answer to work out the volume.
Evaluate Steph’s method.

[2 marks]

First, ignore Steph and work it out yourself. Then point out the differences in your method and Steph's method and say why his answer is the same or is different to your answer

Reply 4

Baza2002

19

Original post by GCSE_18

Steph is solving a problem. Cube A has a surface area of 150 cm2 Cube B has sides half the length of cube A

What is the volume of cube B?

To solve this problem, Steph decides to:
- halve the surface area
-calculate the square root of the answer then divide by 6
- then cube this answer to work out the volume.
Evaluate Steph’s method.

[2 marks]

You know a cube has 6 sides, so do 150 divided by 6 and you have the area of 1 side. you should be able to do it from there

Reply 5

username2857056

OP

11

Original post by Baza2002

You know a cube has 6 sides, so do 150 divided by 6 and you have the area of 1 side. you should be able to do it from there

Thank You, however, I need help on how to do Steph's method without a calculator (i looked at the mark scheme but find it hard to understand it).

(edited 6 years ago)

Reply 6

Lemur14

Volunteer Section Leader

21

Original post by GCSE_18

Steph is solving a problem. Cube A has a surface area of 150 cm2 Cube B has sides half the length of cube A

What is the volume of cube B?

To solve this problem, Steph decides to:
- halve the surface area
-calculate the square root of the answer then divide by 6
- then cube this answer to work out the volume.
Evaluate Steph’s method.

[2 marks]

Hi there