Find the LCM (Lowest common factor) of both numbers.
So, 1.2 x 4 = 4.8
1.6 x 3 = 4.8
We now have the same amount of ground beef for each cost. So for 1.2 lb of beef we do, 4.55 x 4 = 18.2 (£18.20)
And then 6.30 x 3 = 18.9 (£18.90)
So, 1.2 lb package of ground beef is the better buy.