- Let vector a =î+j+k, vector b =î and vector c =c1 î + c2 j+ c3 k then if c2 =-1 and c3 =1 find c3 which no value of c1 can makes vector a ,b and vector c

A girl of height 90cm is walking away from the base of a lamp post at a speed of 1.2m/sec. If the lamp is 3.6m above the ground, find the length of her shadow after 4 sec.
A train takes 2 hours less for a journey of 300 km if it's speed is increased by 5 km/h from its usual speed. Find the usual speed of the train