In a bag, black tablet covers and white tablet covers are in the ratio  5 : 9. If there are 450 white tablet covers, how many black tablet covers are there in the bag?

200 275 225 250

250

Black cover  :  White cover       5           :       9                            ↓                           450(given) 9r = 450 or r = 50  Black tablet covers = 5r = 5 x 50 = 250