Aptitude - Height and Distance - Discussion
Discussion Forum : Height and Distance - General Questions (Q.No. 4)
4.
An observer 1.6 m tall is 203 away from a tower. The angle of elevation from his eye to the top of the tower is 30°. The height of the tower is:
Answer: Option
Explanation:
Let AB be the observer and CD be the tower.
Draw BE 
CD.
Then, CE = AB = 1.6 m,
BE = AC = 203 m.
| DE | = tan 30° = | 1 |
| BE | 3 |
 DE = |
203 | m = 20 m. |
| 3 |
CD = CE + DE = (1.6 + 20) m = 21.6 m.
Discussion:
18 comments Page 2 of 2.
Akshaya Prasad Sahoo said:
8 years ago
Why are you using tan 30?
Monu_yadav said:
8 years ago
But the unit of 20√3 is not given in a problem. So,answer is None of these.
(1)
Mahksh said:
8 years ago
There is no specific rule for this.
According to the situation we have to find this. Here, in this case, DE/BE i.e. perpendicular upon base means "tan".
So we take tan 30.
According to the situation we have to find this. Here, in this case, DE/BE i.e. perpendicular upon base means "tan".
So we take tan 30.
Jatin007 said:
8 years ago
Applying tan because of we need to find DE.
So tan 30= DE/BE.
tan 30=DE/20√3,
DE=20√3*tan30( value of tan 30=1/√3),
So DE= 20.
So CD= EC+ED=1.6+20=21.6(answer).
So tan 30= DE/BE.
tan 30=DE/20√3,
DE=20√3*tan30( value of tan 30=1/√3),
So DE= 20.
So CD= EC+ED=1.6+20=21.6(answer).
(2)
Ravina said:
8 years ago
I too had the Same doubt @Priya.
Please clear the doubt of as.
Please clear the doubt of as.
Priya58310 said:
9 years ago
Why they applied ''tan" what is the rule behind that?
Anurag said:
9 years ago
Here DE/BE = 1/root3.
So, DE will be cross multiply by roo3 and BE will be multiplied by 1.
So, how come the value of DE is divided by root 3?
So, DE will be cross multiply by roo3 and BE will be multiplied by 1.
So, how come the value of DE is divided by root 3?
Yazhini.M.R said:
1 decade ago
Since tan thetq= opposite/adjacent , tan 30= DE/BE ,
the value of tan 30 is 1/ root 3,
then DE/BE=1/root 3, then DE=BE/root 3,
thus 20 m is obtained.
since CD= CE+DE, 21.6 is obtained.
the value of tan 30 is 1/ root 3,
then DE/BE=1/root 3, then DE=BE/root 3,
thus 20 m is obtained.
since CD= CE+DE, 21.6 is obtained.
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