IGCSE starting on Friday... pls.post doubts, important notes etc.

[Stancy Motha]

Three similar solid cones are made of plastic,wood and plastic. The perpendicular heights of the cones are 1m,2m and 3m respectively.

Calculate the ratio..................(volume of wood) : (volume of plastic),
giving your answer in its simplest form

 

[Min Thaw]

is that 8:1?

 

[Stancy Motha]

nope

1:2:3
1:8:27............(cube the previous so we get ratio for the volumes)
8:28
2:7

 

[Min Thaw]

arghhhh.. yeah... you are right..

 

[Min Thaw]

any more?

 

[Stancy Motha]

yup I will keep posting wen I cum across imp ones..

 

[Stancy Motha]

A quadrant has area 100m^3
Find in m, to 3 sgf
a)the radius of the quadrant
b)the perimeter of the quadrant

easy one

 

[Min Thaw]

is that 100m^2 or 100m^3?

 

[Min Thaw]

r = 11.3m
perimeter = 40.3 m
is it correct?

 

[Stancy Motha]

yup next one..
The capacity of a fuel tank is 80 litres of fuel. When the tank is 30% full,Mohammed fills it to its full capacity. The cost of fuel per litre is 65 pence.
Calculate in pounds,how much Mohammed spends.

 

[Min Thaw]

it would probably be 36.4

 

[Stancy Motha]

A regular hexagon has side 6cm.Calculate the area in cm.

 

[Min Thaw]

93.5cm < 3 s.f >

 

[Stancy Motha]

sorry that's wrong
ok draw a hexagon on a peice of paper,now remember it's a regular hexagon
now divide into 6 triangles, now a concentrating on a single triangle, it will be an equilateral triangle because the hexagon is regular, and all sides of the triangle will be 8cm
now area of one triangle=0.5*8*8*sin60............(dont get confused by the * I meant to multiply)
now area of 6 triangles=6(0.5*8*sin60)
the answer is=166cm^2

 

[Min Thaw]

well..okay..your method is fine...but here's what i do..
i divide it into two isosceles triangles and a rectangle...and find the area using 2<o.5*6*6*sin120> + rectangle area

and one question why is the side of triangle 8 cm? is that not 6?

 

[Stancy Motha]

Given that sinx=0.5 and 0<x<90
a)WITHOUT USING CALCULATOR,show than tan x=1/(root3)
b)express root 3 cos x as a fraction.

 

[Stancy Motha]

[why is the side of triangle 8 cm? is that not 6? ]
oopsie my apologies ...the question supposed to be 8cm.
and u'r methods better than mine...
u'r ans right that way...U'r gud
have any question for me??

 

[Min Thaw]

sinx = 0.5
x = 30
sinx = 0.5
sinx / cosx = 0.5 /cos x
tan x = o.5/cos 30
tan x = o.5/ (root3 /2)
tanx = 1/root3

b. 3/2

 

[Min Thaw]

[why is the side of triangle 8 cm? is that not 6? ]
oopsie my apologies ...the question supposed to be 8cm.
and u'r methods better than mine...
u'r ans right that way...

your method is great too... i love solving maths with different alternatives..and your is awesome

 

[Stancy Motha]

s=20+54t-t^3
a)Find the distance moved in the 3rd second