Which is more suitable in teaching of science?

1 In an alloy, zinc and copper are in the ratio 1 : 2. In the second alloy, the same elements are in the ratio 2 : 3. If these two alloys be mixed to form a new alloy in which two elements are in the ratio 5:8, the ratio of these two alloys in the new allow 2 A and B can complete a piece of work in 80 and 120 days respectively. They together start the work but A left after 20 days. After another 12 days C joined B and now they complete the work in 28 more days. In how many days C can complete the work, working 3 Train A takes 45 minutes more than train B to travel a distance of 450 km. Due to engine trouble speed of train B falls by a quarter, so it takes 30 minutes more than Train A to complete the same journey. What is the speed of Train A (in km/hr)? 4 X and Y are two alloys which are prepared by mixing zinc and aluminium in the ratio of 1 : 4 and 11 : 8 respectively. If equal quantities of alloys are melted to form a third alloy Z then what is the ratio of zinc and aluminium in alloy Z? 5 The distance between two places, A and B, is 300 km. Two riders, on scooters start simultaneously from A and B towards each other. The distance between them after 2.5 hrs is 25 km. If the speed of one scooter of one scooter is 10 km/hr more than the other