You are Here: Home >< Maths

# GCSE Maths Question watch

1. Struggling to understand it

Thanks!
Attached Images

2. i will give you hints for a) and b)..

When you think of scale factor, think of the ratios of corresponding "measuements" of "similar" objects, like sides or height.

a) The key words in the question are: "...what is the scale factor of the lengths of the large cone to the small cone"

i.e. what is the ratio of any available measurement of length in the large cone to a corresponding one in the small cone?

What about the height? - the question tells us that the large cone is 15cm in height, and the frustrum is 10 - leaving 5, so scale factor of "large to small"

is i.e. large height to small height ("small to large scale factor is just the reciprocal of this)

for b) if the scale factor of length is "m" , say, the scale factor of surface area will be

i.e. the large cones surface area will be times bigger than the smaller ones, and the small one`s is already given - (careful! - need to clarify if this is entire or lateral surface area)

The (entire, including base) surface area of a cone is (just the 1st bit multiplied out if lateral area)

Lateral surface area is:

To get the surface area of the large cone, multiply the surface area of the small one by the area scale factor...

which you obtained from the above ratio...

(As a check, put both in the ratio of "large cone area to small cone area, and you should get the correct factor - hint: 9)

(EDITED)

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: January 25, 2015
Today on TSR

### Struggling to get going with your revision?

Get going with the all day revision thread

### Uni strikes! How do they affect you?

Discussions on TSR

• Latest
Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE