Selina Solutions Class 9 Mathematics Solutions for Exercise 6(G) in Chapter 6 - Chapter 6- Simultaneous Equations

Question 6 Exercise 6(G)

90% acid solution (90% pure acid and 10% water) and 97% acid solution are mixed to obtain 21 litres of 95% acid solution. How many litres of each solution are mixed?


Let the quantity of 90% acid solution be x litres and

The quantity of 97% acid solution be y litres

According to the question,

x + y = 21...(1)

and 90% of x + 97% of y = 95% of 21

Video transcript
"hello guys welcome back to the room work i'm ravan kumar working as a tutor that pluto so today we are going to solve one really very interesting question so let's see how we can do it and now we can solve here so they have given that 90 percentage of a acid solution is prepared that is 90 percentage of pure acid and 10 percentage of water so that is 90 percentage of acid solution and 97 percentage of another acid solution are mixed to obtain 21 liters of 95 percentage of acid solution so that means so first acid so let's assume that first acid be x liters okay and the second acid be y liters okay so they have mixed with x plus y to get 21 liters okay so 21 liters of acid so this is our first equation let's consider and the second one 90 percentage of x 90 percentage 90 by 100 into x plus 97 percentage of y right 97 by 100 into y is equals to 21 liters 95 percentage off that is multiplied by 21 so here hundred and hundred and hundred will be getting cancelled and the the second equation you will be getting 90 x plus 97 y is equals to that is 9 1995 right so this is our second equation now to this first equation multiplied by 90 here so after multiplying by 90 you will get the first equation as 90 x plus 90 y is equals to eight one thousand eight hundred and ninety so this is our first equation and then here 90 x plus 97 y is equals to 1995 these are the two equations here so just subtract here so this end this will be cancelled and then here also subtraction will be done minus seven y is equals to here minus one not phi you will get right so y is equals to how much so y is equals to 21 you will be getting the y is equals to 21 so what is the x here so x plus y is equal to 21 right so x plus okay so it will be y is equals to 21 and then yep so yep so actually y is equals to 15 okay so y is equals to 15 so actually 7 into 15 only the one or two right so 15 seven zero not right so that is why y is equal to 15 so x plus 15 is equals to 21 and then x is equals to 6 so i hope you understand what i've done here if you have any doubts please comment below don't forget to subscribe to this channel thank you so much for watching and stay tuned thank you"
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