A triangular field,the sides of which measure 32 yards,48 yards,and 60 yards,has a number of trees,each occupying an area of `sqrt(1463)` sq.yards.Then the number of trees in the field are (Assume that no two trees have common area & there is no room without a tree)
A) 30 B) 18 C) 16 D) 20

21 mango trees, 42 apple trees and 56 orange trees have to be planted in rows such that each row contains the same number of trees of one variety only. Minimum number of rows in which the trees may be planted is (a) 3 (b) 15 (c) 17 (d) 20

Perimeter of a rectangular field is 160 metres and the difference between its two adjacent sides is 48 metres. The side of a square field, having the same area as that of the rectangle, is (a) 4m (b) 8m (c) 16m (d) 32m

Along a yard 225 metres long,26 trees are planted at equal distances,one tree being at each end of the yard.What is the distance between two consecutive trees? (a) 8 metres (b) 9 metres (c)10 metres quad (d) 15 metres

On a 2 km road, a total number of 201 trees are planted on each side of the road at equal distances. How many such trees in all will be planted on both sides of a 50 km road such that the distance between two consecutive trees is the same as that of the consecutive trees on the 2 km road? (a) 501 (b) 5000 (c) 5001 (d) 5025 (e) 5050

Answer the following question:- Noise is a common problem in both urban and rural areas, traffic noise in particular. Trees and shrubs are not only visually attractive but also can make effective noise barriers. Therefore when space permits we have to plant more trees and shrubs in areas where there is noise problem. By doing this noise can be reduced by six decibels over a distance of 30 metres. The only thing we have to keep in mind is that the planting should be particularly dense, the trees which have dense foliage and relatively vertical orientation of arrangements should be planted. It will completely screen the source of noise. If there is any gap in barrier it will still allow noise to penetrate. Single layer of trees is worthless as a noise barrier. Due to inter-reflection, multi-rows of trees are more effective. What distance a good number of trees can cover in reducing noise ?

A current i, indicated by the crosses in figure, is established in a strip of copper of height h and width w. A uniform field of magnetic induction B is applied at right angle to the strip. (a) Calculate the drift velocity v_d of the electrons. (b) What are the magnitude and direction of the magnetic force F acting on the electrons? (c) What should the magnitude and direction of a homogeneous electric field E be in order to counterbalance the effect of mangetic field? (d) Calculate voltage V necessary between two sides of the conductor in order to creat this field E Between which sides of the conductor would this voltage have to be applied? (e) If no electric field is applied from the outside, the electrons will be pushed somewhat to one side and therefore will give rise to a uniform electric field E_H across the conductor until the forces of this electrostatic field E_H balance the magnetic forces encountered in part (b). What will be the magnitude and direction of field E_H ? Assume that n, the number of conductor electrons per unit volume is 1.1xx10^(29) m^-3, h = 0.02 m, w= 0.1 cm, i = 50 A, and B=2 T.