Problem Solving

Look at the below. Two variables. One equation. How would you clou in that there is only possible answer and that the info is suff?

the attachments in this post are quite large. I am reattaching as word documents. Also, apologies for incorrectly putting this into the PS Forum

23 cent pencils & 21 cent pencils

23 cent pencils ?

Statement I

total number of pencils 6
we dont know the exact amount.

insufficient.

Statement II

total amount 130

21x + 23y = 130


remember x and y has to be integers and after multiplying the unit digits should add to 0.

This can only be done one way

when x=4 and y=2

21*4 = 84
23*2 = 46

84+46=130

Sufficient.

Hence B is the answer.

all the best.

LSB wrote:the attachments in this post are quite large. I am reattaching as word documents. Also, apologies for incorrectly putting this into the PS Forum

statement 1 . insufficient

statement 2 . since 130 is not a factor of either 23 or 21... she would have definitely atleast 1 of each pencil.

now we know 130/23 <n< 130/21

n must be a integer so its 6.

assume she bought X pencils for 23 cents..

she wud have bought 6-X for 21

therefore

23x + 21 ( 6 – x)= 130

hence X = 2.

hence B

Hope that helps

Makes sense. I guess you can convert the equation into having one variable. I got the right answer (it was a sledgehammer approach though)

Was just unsure how we can have only one equation that solves for two variables. Thanks guys.

I think the key thing to realise here is that this question is also testing your knowledge of digits ... as parallel_chase pointed out.

Essentially, with statement 2 we have to figure out how many 23's and how many 21's we can fit into 130.

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