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There are 3 times as many pens as erasers. The ratio of the number of erasers to the number of rulers is 3 : 2. There are 28 more pens than rulers. How many pens are there?

 

(1)      8

(2)      36

(3)      56

(4)      84

 May 19, 2021
 #1
avatar+119907 
+1

Let   the  number  of   pens  =  3x

Let the  number  of erasers  =  x

Let  the  number  of  rulers  =  3x  - 28

 

And  we  know  that

 

x / ( 3x - 28)  =   3/2           cross-multiply

 

2x  =  3(3x - 28)         simplify

 

2x  =  9x  -  84        rearrange  

 

9x - 2x  =  84

 

7x  =  84

 

x =  84 / 7     =    12  =  number  of erasers

 

Number of  pens  =  3x   =  3(12)  =    36

 

 

cool cool cool

 May 19, 2021

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