UPSC 2013 CDS 2 Math Paper

4 goats = 6 sheep ⇒ 2 goats = 3 sheep.
So, 2 goats and 9 sheep = 3 sheep + 9 sheep = 12 sheep (equivalent)
Now, number of days for 6 sheep to graze the field = 50 days
Therefore, the number of days required for 12 sheep to graze the field =

50×6

12

=25
So, 2 goats and 9 sheep can graze the field in 25 days.