Question 1040918
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An insecticide contains 65 centigrams of inert ingredient for every 1 centigram of active ingredient. 
If a quantity of insecticide weighs 528 centigrams how much of each type of ingredient does it contain
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Group-regroup you total mass of 528 centigrams in smaller groups each containing 65 centigrams of inert ingredient and 
   1 centigram of active ingredient. 

According to the condition, it is possible to do (!).

How many groups will you have? Obviously, {{{528/66}}} = 8 groups, where 66 = 65+1 is the mass of each group.

Thus you have 8*65 = 520 centigrams of inert ingredient and  8*1 = 8 1 centigram of active ingredient. 
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Solved.