Elitmus
Exam
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if A moves to the distance X,then turn 120 degree and travel to X and again turn 120 and travel x ,he is 9 inches from starting point,what is the value of x??
A)3root(3)
b)9root(3)
C)i can't remember
Read Solution (Total 10)
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- First let u start from from one point S(Source) travelling x distance in north direction,now u need to move 120 degree so first take 90 left u are in west direction & again remaining 30 direction left(i.e anticlock direction) now u r facing south west.Now move x distance in south west direction.
Now u need to move right 120 degree(BE CAREFUL). ie 120 degree clockwise (U will see it will again point in the north direction).At ur room please use scale and protractor to get clear diagram.Now move x distance in north direction let u reached point F(Final).
Now join S and F.So SF=9 given. U will see u will get 2 similar triangle.
(F) .
. .
. . .(A)
. . (M) . .
. . .
. . . .
(B) . . .
.(S)
ROUGH DIAGRAM
1.U start from S move AS=x.(north direction)
2.Turn 120 degree left(anticlockwise),move AB=x.(south west direction).
3.Turn 120 degree right(clockwise) u will again pointing to north direction.(Since 120 right & again 120 degree left nullify each other)
4.Move BF=x.
5. FS=9(given).
U will see M bisext both FS & AB.
TRY URSELF u will find angle MAS=60 degree.Since BF and AS are parallel so angle MAS and FBF are same equal to 60 degree.
Since both triangle are similar.So u can apply cosine angle formula to any one to get x.
For eg
In triangle FBM
FM=9/2=4.5, BF=x & BM=x/2.
So cos 60=(x)square+ (x/2) square-(4.5)square
-------------------------------------------------
2*x*(x/2)
U will get x(square)=81/3.
Taking root and rationalizing u will get x=3*root3
I take north as my starting point u can take any direction as per ur choice.HARE KRISHNA - 9 years agoHelpfull: Yes(4) No(1)
- correct qstn is-
if A ant moves to the distance X,then turn left 120 degree and travel to X distnce again nd turn right 120 and travel x ,he is 9 inches from starting point,what is the value of x??
soln-it will make a parallelogram, aftr that we will see that both triangle is eguilateral triangle , then all sides of parllelogram is x nd one diagonal is x nd another diagonal is 9. Then by the proprty of parellelogram-
sum of diagonals square(d1^2 +d2^2)=sum of square of sides(AB^2 +BC^2 +CD^2 + DC^2)
then-
x^2 +9^2 =x^2 +x^2 +x^2 +x^2
x=(9/root3)=3root3
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')60____________ - 9 years agoHelpfull: Yes(4) No(0)
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- it will make a parallelogram, aftr that we will see that both triangle is equilateral triangle , then all sides of parallelogram is x nd one diagonal is x nd another diagonal is 9.
By parallelogram rule .. Ans is 3root3 - 9 years agoHelpfull: Yes(0) No(0)
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