question_answer4) A bag contains white, black and red balls only. A ball is drawn at random from the bag. If the probability of getting a white ball is \[\frac{3}{10}\] and that of a black ball is \[\frac{2}{5}\] then find the probability of getting a red ball. If the bag contains 20 black balls, then find the total number of balls in the bag.
question_answer5) A truck covers a distance of 150 km at a certain average speed and then covers another 200 km at an average speed which is 20 km per hour more than the first speed. If the truck covers the total distance in 5 hours/ find the first speed of the truck.
question_answer7) Construct a triangle ABC in which \[AB=5\text{ }cm,\text{ }BC=6\text{ }cm\] and \[\angle ABC=60{}^\circ \]. Now construct another triangle whose sides are \[\frac{5}{7}\] times the corresponding sides of \[\Delta \text{ }ABC\].