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

Question 7 Exercise 6(F)

A and B both have some pencils. If A gives 10 pencils to B, then B will have twice as many as A. And if B gives 10 pencils to A, then they will have the same number of pencils. How many pencils does each have?

Answer:

Video transcript
"hello guys welcome back to leader homework i'm leaving kumar working as a tutor at video so today we are going to solve and explore one more really very interesting question so let's see how we can do it okay so now a and both are persons both have some pencils okay so now if a gives 10 pencils to b then b will have twice as many as a okay so now observe properly let's assume a as the x number of pencils and b as y number of pencils now what is the first condition they have given here a gives 10 pencils to b then b is a b half twice as number of like as many as a so if a is giving 10 pencils so it will become is equals to x minus 10 right so if it is x minus 10 so this will be 2 of x minus 10 so that it will it will be like gaining some pencils so this is only our equation that is y plus 10 is equals to 2 of x minus 10 right so this is our first equation here then so and if b gives 10 pencils to a then they will have the same number of pencils so the second equation here is when the b gives that is y minus 10 is equals to x plus 10 so this is our second equation so now let's solve this both here so y plus 10 is equals to 2x minus 20 so if you are taking this all to this side so you will be getting the answer as so 2x minus 2x minus y is equals to 30 you will get okay so 2x minus y is equals to 30 this is our first equation and here you will get the answer as x minus y is equals to uh how much you will be getting x minus y is equals to minus 20 you will get here right so now that is the thing so now let's do your problem so let's do solve these two equations here so we can solve 2x minus y is equals to 30 and here in this end so you will be getting x minus y is equals to minus 20 right so now so just subtract here each and everything so 2x minus x is equals to x and here it minus into minus it will become plus right so this and this will be getting cancelled and the x is equals to here minus into minus plus it will become so it will become x is equals to 50 right so x is equals to 50 then what is the value of y so let's substitute it in any of the equation here so that is x minus y is equals to minus 20 so 550 minus y is equals to how much minus 20 right so then y is equal to how much 70 right so x is equals to 15 y is equals to 70 that is our final answer here so i hope you understood what i've done if you have any doubts please comment below don't forget to subscribe to this channel thank you so much for watching this stay tuned"
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