13. A group of 210 men had provisions for 60 days. After 10 days, 60 men left. How long will the remaining food last?

Hi, 
There is no Q-15 so answering last one:
Given that Total men = 210 and they had provisions for 60 days.

Therefore the total available food = 210 * 60

                                                          = 12600

Given that After 10 days, 60 men left.

Then the food consumed for 10 days = 210 * 10

                                                               = 2100.

Now, the available food = 12600 - 2100

                                         = 10500.

Remaining men = 210 - 60

                           = 150.


Therefore the remaining food lasts for 10500/150 = 70 days.