Alloy A has 80% copper and 20% tin. A certain process when applied repeatedly to the alloy decreases the copper quantity in the alloy by one-fifth and the tin quantity in it by one-tenth, each time it is applied. The minimum number of times the process must be applied so that the concentration of copper in the alloy is less than 70% is ____.
a)4
b)5
c)3
d)2
2 comments
The answer is 5. Approach please!
the thing with ratio and proportions is they r Consistent, after applying the process once the cooper would be 78%, i.e 2% drop... assuming 2.5 as an average we have to apply the process at least 5 times to get it less that 70%..