A boy standing on a ground sees an angle of elevation of 30° to the top of a tower 50 m high . When he started walking towards tower in a straight line, after 3 minutes he observes an angle of elevation of a top of a tower as 60°, then walking speed of a boy is
Let distance walked by boy from starting point where he observes an angle of elevation 30° and the point where he observes angle of elevation 60° be 'x' m and the distance of base of a tower from starting point be 'y' m.
Then, trignometric ratios:
tan 30 = 50/y
1/√3=50/y ⇒ y=50√3 ---(i)
Also, tan 60 = 50/(y-x)
√3=50/(y-x) ⇒ y-x=50/√3 ---(ii)
Substituting value of y from (i) into (ii), we get x=100√3
Now, the distance travelled 'x' in 3 minutes is 100/√3 m, so distance/hr=(60/3)*100/√3=1154.7 m
Speed=1.1547 km/hr
Correct Option 7)
The difference between a two-digit number and the number obtained by interchanging the digits is 36. What is the difference between the sum and the difference of the digits of the number if the ratio between the digits of the number is 1 : 2 ?