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[crystal.s]

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hey calcie.

now im not 100% sure if this is how you work your question out. BUT the angle of elevation is equal in size to the angle of depression, as alternate angles are equal.

so angle M=75* .

to find out the elevation i THINK you just divide that 75* by 2. so angle of elevation=38*

but i dont get why they have the measurements JK and MK. maybe its to try and confuse us. or i just dont get it either and im completely wrong lol

do you know what the answer is?

[calcie]

the answers say 58*

lucky i still have a bit of time before HSC to attempt to learn all of this.

[tacogym27101990]

Originally Posted by calcie

the answers say 58*

lucky i still have a bit of time before HSC to attempt to learn all of this.

if you still need help with it:
angleMJK = 15*
so using the sine rule: sin15/mk = sinJMK/JK
sin15/18=sinJMK/20
sinJMK= 20sin15/18
so JMK = 16*43'
therefore KML = 75* - 16*43'
=58* (nearest degree)

[calcie]

thanks heaps
i new it would of had to be something relatively simpleish

[hsc100]

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Does anyone know the answers and working out to these general mathematics problems? If so can you plz help

1. A cylindrical wheat silo is 40m high and 20m in diameter

a) If paint covers 8m square per litre, find the number of 10 litre cans of paint needed to paint the silo with one coat?

b) Paint costs $115.20 per 10 litre can.find the cost of the paint for the silo


2.How many spheres of 15cm diameter can be covered by 10m square of material


3.Determine the total area of leather in 20 dozen cricket balls each with diameter 7cm

[Timothy.Siu]

1. A cylindrical wheat silo is 40m high and 20m in diameter

a) If paint covers 8m square per litre, find the number of 10 litre cans of paint needed to paint the silo with one coat?

b) Paint costs $115.20 per 10 litre can.find the cost of the paint for the silo




for a) the diameter is 20m so the circumference is pi x 10^2=100pi
and the height is 40m high
so the surface area of the round "walls"is 40x100pi units squared
i'm assuming u dont have to paitn the top and bottom, but that would just be pi x r^2

10 litres of paint can paint 80 square metres, so 100pi/80 is less than or equal to the number of cans of 10 litre cans, 400pi/80=3.926.......wich u round up to4
b)4x115.20=$460.8

[Timothy.Siu]

2.How many spheres of 15cm diameter can be covered by 10m square of material

surface area of sphere is 4pi x r^2
r=7.5
total surface area of one sphere is 7.5^2x4xpi=225pi.cm squared
10m squared=100000cm squared (i think)
100000/225pi=141.4....
wich means u can only cover 141 spheres


3.Determine the total area of leather in 20 dozen cricket balls each with diameter 7cm

this is surface area again,
same formula SA(sphere)=4pi x r^2
r=3.5 SA=49pi cm squared

49pi x 20=980pi cm squared

[Bethybo]

yes that would be really good

[*Cassie*]

hey does anyone know how to put algebra equations into your graphics calculator?
and also in an exam can we just write the asnwer from the calculator adn get full marks?

[PC]

Originally Posted by *Cassie*

hey does anyone know how to put algebra equations into your graphics calculator?
and also in an exam can we just write the asnwer from the calculator adn get full marks?

In General Maths, it's pretty straightforward. Go into the Equation Mode [A], press [F3] for solver, and type in your equation. You can usually type it as you see it. Equations with fractions are a little more difficult. Just put brackets around the numerators and denominators. Then scroll down so that the letter that you're trying to find is highlighted. It will probably show 0 or sometimes a strange number. This is NOT the solution. You MUST press [F6] to solve the equation.

[*Cassie*]

Great thanks it worked!!! thankyou
Also i cant do these equations with sqaure roots
3(Squareroot) m- 4= -1
the m-4 is in the square root only
i can do the others ones how you just square it to cancel out the square root but i don't know how to do it when theirs a number outside the square root..
thanks

[stolenhotelpen]

I am having trouble with a question in Data. I can never seem to remember how to find the Standard Deviation when there is classes (continuous data).

The table has this info:

0-4 | 5
5-9 | 6
10-14 | 8
15-19 | 7
20-24 | 4


Question says:
"use the class centres to find the population standard deviation for the grouped data given".

Any help would be much appreciated. I just can't seem to get the answer.
Oh, and another question.. when you are doing Trig with right-angled triangles, and you are finding an unknown angle, what are the steps in entering it into a calculator. (I've got the old Casio one). I keep getting maths error or syntax error... >< ??

[nerdsforever]

0-4 | 5
5-9 | 6
10-14 | 8
15-19 | 7
20-24 | 4

Firstly, find the class centes. The class centre for class 0-4 would be (0+4)/2 = 2.... class 5-9 would be (5+9)/2 = 7.... etc
Then use your calculator to do standard deviation. enter the class centre, then the frequency.

For finding unknown angles, SHIFT sin and then 0.0001 or whatever the number is.