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The sum of three numbers $a, b$ and $c$ is 60. If we decrease $a$ by 7, we get the value $N$. If we increase $b$ by 7, we get the value $N$. If we multiply $c$ by 7, we also get the value $N$. What is the value of $N$?

 Apr 27, 2022
 #1
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a +  b + c =  60

 

N = a - 7   ⇒   N + 7  =  a

N = b + 7  ⇒   N - 7   =b

N = 7c    ⇒     N / 7  =  c

 

So

 

(N - 7)  + ( N + 7)  +  N  /7  =   60

 

2N  +  N /7   =  60                      multiply through by 7

 

14N + N  =   420

 

15N  = 420

 

N =  420  /  15     =     28

 

 

cool cool cool

 Apr 27, 2022
 #2
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Thank you!

Guest Apr 27, 2022

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