Example A pharmaceutical dealer has 200 gms. of insecticide of 30% concentration. He adds to it some quantity of 5% concentrated insecticide and obtains a mixture of 10% concentration. What quantity of 5% concentration did he add ?

Solution : You are looking for the quantity of 5% concentration of insecticide he added.

Let it be x gms.

Solution- I + Solution - II = Mixture
Weight of solution	200 gms	x gms	(200 + x) gms
% of solute	30 % +	5 %	= 10 %
Weight of solute

Thus, we have set up an equation as

6000 + 5 x = 2000 + 10 x

6000 - 2000 = 10 x - 5 x

4000 = 5 x

800 = x

Therefore the weight of insecticide of 5% concentration was 800 gms.

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Index

9.1 - Definition and Solving Techniques
9.2 - Use of Simultaneous Linear Equations

Chapter 1