A milkman has 80% milk in his stock of 800 litres of adulterated milk. How much 100% pure milk is to be added to it so that purity is between 90% and 95%. How much pure milk should he add to his stock to obtain 99% of pure milk ? What should be done to stop adulteration in foods?

Adulterated milk contains 80% pure milkAmount of pure milk in 800 litres of adulterated=80100×800=640 litresLet the amount of pure milk added to 800 litres of adulterated milk  be x litres.The milk content of the mixtured form=Amount of pure milk contentTotal volume of the mixture×100=x+640800+x×100=100x+64000800+xFirst,90<100x+64000800+x<9590800+x<100x+64000<95800+x72000+90x<100x+64000<76000+95xConsider100x+64000<76000+95x5x<76000-640005x<12000x<2400Now consider72000+90x<100x+6400010x>72000-6400010x>8000x>800Hence, 800<x<2400Now if purity is to be made 99%100x+64000800+x=99100x+64000=99x+79200x=79200-64000x=15200

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