IGCSE/GCSE/O & A Level/IB/University Student Forum
Qualification => Subject Doubts => IGCSE/ GCSE => Math => Topic started by: godfather93 on May 16, 2009, 09:49:14 pm
-
can someone please explain this question to me? this question has got me completely spinning.
-
sure.. but which one?
-
sorry forgot to put the question!! :-[
Question 9
-
the percentage of the total area which is shaded = shaded area/total area of the figure x 100
the fraction of the total shaded area = shaded area/total area of the figure
-
Yea thats a tricky one.. i dont think theyl bring somethin like that this year cuz its kinda old..
but for the first one.. its 1/4 * 100= 25% i think its straighforward..
and the rest ima need a pen and paper to get it goin :-\
and By the way.. wat was question 6? also weird.. very hard..
-
but how did you get the shaded area?
-
astar please help! ???
-
get the shaded area in terms of h .. then the total area in terms of h .. and divide .. the h will get canceled
for the first diagram => answer is (0.5 x 1 x h) / (0.5 x 4 x h) x 100 = 1/4 x 100 = 25%
for the second diagram => (0.5 x 1 x h) / (4 x h) x 100 = 1/8 x 100 = 12.5%
got it?
-
i totally get it. Thank you very much. I was using the same method as you showed above before but i was making a very stupid mistake. I took the area, especially, of the triangle as being 1/4*b*h insteas of 1/8*b*h.
Thank you once again! (+rep)
-
ur welcum ;)
-
9a)25% since A=0.5base*height and the heights are the same.
b)12.5 since A=base *height for the paralellogram and 1/5base*height for the triangle
c)37.5 since if you cut the kite in half downwards the base is in the ratio 1:3 so shaded area is 75% of the triangle the half this
d)Divide the traezium into 3 triangles then ans=60%
-
bi)20/180*100%
ii)pi*1^2/pi*5^2*100%=4%
ii)(pi3^2-pi2^2)/pi3^2=5/9=55.6%
-
thanks! :D I understand the question now. I was making a silly mistake.
-
oh. I'm stuck again at the same question. I don't get how to calculate the shaded area of diagram 4. That is a bit tricky.
-
dude stop stressin urself out.. this paper was ages ago its unlikely a question like that will come up..
they like to put a lil sequences ques at the end lately and theres many topics that didnt come on p2 that MUST come on p4 so theres no room for silly questions like these ::)
-
The base of the trapezium is 3 times the base of the triangles, so cut the trapezium up into 3 equal triangles and EVERY triangle has the same area whether shaded or not.
-
divide the shaded trapezium into 3 triangles
now all the small triangles would be equal .. so the % would be 3/5 x 100 = 60%
the 3 is the shaded and the 5 is the total number of triangles
-
how do you know the base of the trapezium is 3 times the base of the triangles?
-
dude stop stressin urself out.. this paper was ages ago its unlikely a question like that will come up..
they like to put a lil sequences ques at the end lately and theres many topics that didnt come on p2 that MUST come on p4 so theres no room for silly questions like these ::)
how can you be so sure this question won't come up? You never know what may come up and it's better to clear your doubts before the exam.
-
dude stop stressin urself out.. this paper was ages ago its unlikely a question like that will come up..
they like to put a lil sequences ques at the end lately and theres many topics that didnt come on p2 that MUST come on p4 so theres no room for silly questions like these ::)
and by the way this is no silly question cause it is challenging and not many people can do this question.
-
Because the height of the trapezium and the triangles are the same.
-
how does that make the bases the same ?
-
look at the attachment i put .. the bigger triangle which is circled in red has its 2 sides divided equally .. and the base of the upper side of this triangle is parallel to the base of the bigger triangle .. and is similar to it
-
ahhhhh... now i get it!!! thanks so much for the help astar and twilight.
-
Sorry the base of the trapezium is twice the base of the triangle but the area is still 3 times.
-
the base AB and EC are in the ratio 2:1 because AD and ED are in the ratio 2:1 .. so its because of the similarity