Two train approach each other at 30 km/hr and 27 km/hr. From two places 342 km. apart. After how much time will they meet? (in hours)

The ratio of two numbers is 4:5 and their LCM is 120. The numbers are

Pipe A can fill a tank in 4 hours and pipe B can fill it in 6 hours. If they are opened on alternate hours and if pipe A is opened first then in how many hours, the tank shall be full? 

If 1³ + 2³ + .....+103 = 3025 then 4 + 32 + 108 + ..... 4000 is equal to -

The ratio of efficiency of Arun is to Chitra is 5:3. The ratio of number of days taken by Bala is to Chitra is 2:3. Arun takes 6 days less than Chitra, when Arun and Chitra complete the work individually. Bala and Chitra started the work and left after 2 days. The number of days taken by Arun to finish the remaining work is?