A stone A is thrown at an angle of 45o to the horizontal. Another stone B is thrown with 20 ms-1 horizontally as shown in figure. They collide in mid-air. If distance BCis 4n meter, then the value of n is ____.

vA=uA−gj^ and vB=uB−gtj^∴ vAB=vA−vB=uA−uB =10i^−10j^+20i^=30i^−10j^∴tan⁡θ=13It means relative velocity of A with respect to B is directed at θ with vertically downward direction.For collision, vAB should be towards initial position of B.∴tan⁡θ=BC36∴BC=36×13=12=4n∴n=3