Torch+ battery= 2.50
Torch=battery+1.50
So,
battery+1.50+battery=2.50 therefore,
2 battery = 2.50-1.50;
battery = 1/2=0.50
Since the total price is 2.50 and the battery costs 0.50 then the torch must cost 2.
2/2.50 = 1/1.25 is the fraction the torch costs out of the total costs.