The cost of 8 pencils and 10 rubbers is Rs 60. Find the cost of 4 pencils and 5 rubbers.
cost of 8 pencils and 10 erasers = Rs 60
(as 4 pencils and 5 erasers is exactly half of 8 pencils and 10 erasers)
cost of 4 pencils and 5 rubbers = 60/2 = Rs.30