Quick E maths revision

eagle SG

This kind of question comes out 70+% of the time... Very frequent... Do make sure you know how to do :D

Find
(i) area of triangle ABD / area of triangle CBD
(ii) area of triangle ABD / area of triangle ABC

Something like that...

For those who are not sure, the hint is below:

To crucifixed and pillow, both of you should know how to do le hor...

Oceane SG

This kind of question comes out 70+% of the time... Very frequent... Do make sure you know how to do :D

Find
(i) area of triangle ABD / area of triangle CBD
(ii) area of triangle ABD / area of triangle ABC

Something like that...

For those who are not sure, the hint is below:

To crucifixed and pillow, both of you should know how to do le hor...

Same height, so compare bases.

eagle SG

Same height, so compare bases.

yup, but I realise many times that there are still many pple who dun understand or dunno how to do these type of questions...

Theguiltshow SG

I guess the trick lies in being able to see the common height/base :-)

eagle SG

yup

The question above is the simplest and most basic... Often, you will have these sort of triangles hidden within quadrilaterals and polygons, and at different angles from the above...

crucifiedx SG

yeah. =)

for coordinate geometry, there's one formula to find length right? got some square root thing in the formula de. what's the formula ar? i forgot le.. :X

eagle SG

yeah. =)

for coordinate geometry, there's one formula to find length right? got some square root thing in the formula de. what's the formula ar? i forgot le.. :X

square root of [(x1 - x2)^2 + (y1 - y2)^2]

formula comes from pygathoras theorem

crucifiedx SG

square root of [(x1 - x2)^2 + (y1 - y2)^2]

formula comes from pygathoras theorem

thanks..

then is 0.098 3 sig fig? i v blur..

eagle SG

thanks..

then is 0.098 3 sig fig? i v blur..

2 sig fig, but 3 decimal point

count from right side

crucifiedx SG

so 0.0098 is also 2 sig fig? zeros don't count?

eagle SG

so 0.0098 is also 2 sig fig? zeros don't count?

zeros on the left doesn't count

so 0.000000098 is still 2 sig fig

but 0.00908 is 3 s.f.

0.009008 is 4 s.f.

crucifiedx SG

zeros on the left doesn't count

so 0.000000098 is still 2 sig fig

but 0.00908 is 3 s.f.

0.009008 is 4 s.f.

ok. thanks. (:

eagle SG

oh ya

0.00000980 is also 3s.f.

0.0000000098000 is 5 s.f.

but 98000 can be 2 s.f., 3s.f., 4s.f. or 5 s.f., depending...

crucifiedx SG

ok.. i was looking through my tys then i realised i forgot how to do this ques:

A model of a tanker is made using a scale of 1:20.

(a) the length of the tanker is 15m. calculate the length, in cm, of the model.

(b) the model holds 12 litres of liquid.

calculate the number of litres the tanker will hold.

crucifiedx SG

for (a), i can get the ans but i don't understand.

this is my working for (a):

15m=1500cm

1500/20=75cm

eagle SG

change all to the same unit, then you can safely multiply or divide by 20 here and there

1:20 means 1cm : 20cm or 1 m : 20 m

for part (b), it's volume. so you need to bear in mind the cube required... :D

crucifiedx SG

is the largest side of a triangle facing the largest or the smallest angle?

eagle SG

is the largest side of a triangle facing the largest or the smallest angle?

draw a triangle and see it yourself... you should be able to find the answer.

an alternative method is to look at sine rule to prove, but you need to understand how sine functions... this one dun think you will have learned before

crucifiedx SG

change all to the same unit, then you can safely multiply or divide by 20 here and there

1:20 means 1cm : 20cm or 1 m : 20 m

for part (b), it's volume. so you need to bear in mind the cube required... :D

ok.. but i don't undrestand part (b)..

crucifiedx SG

draw a triangle and see it yourself... you should be able to find the answer.

an alternative method is to look at sine rule to prove, but you need to understand how sine functions... this one dun think you will have learned before

ok.. is it facing the largest angle?