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Re: GMAT Prep few more [#permalink]
22 Feb 2010, 21:58

hello guys, i do not know where to post this problem so i am posting it here.

Laura has 20 coins consisting of quarters and dimes. If she has a total of $3.05, how many dimes does she have?

a. 3 b. 7 c. 10 d. 13 e. 16

i was struggling for more than half an hour but cudn't get the answer, finally i tried with all options and got the correct answer. pls guide. _________________

"Great people don't do different things, they do things differently"

Re: GMAT Prep few more [#permalink]
22 Feb 2010, 23:38

target2011 wrote:

hello guys, i do not know where to post this problem so i am posting it here.

Laura has 20 coins consisting of quarters and dimes. If she has a total of $3.05, how many dimes does she have?

a. 3 b. 7 c. 10 d. 13 e. 16

i was struggling for more than half an hour but cudn't get the answer, finally i tried with all options and got the correct answer. pls guide.

Lets assume Laura has X quarters and Y dimes, then we know X+Y=20 and also 0.25X + 0.1Y = 3.05

solve these and you will get the answer

Another way of looking at it ..!

We know that sum is $3.05 which means number of quarters or dimes will odd, so straight away u can eliminate the even answer options ( 10 and 16 ) now we are left with options 3, 7 and 13, clearly in the left options you can clearly see that 13 can be the only candidate.

Or you can also use the spilt option to make it easy by plugging in use 10 first and you will see that answer has to be greater than 10 ..

Re: GMAT Prep few more [#permalink]
23 Feb 2010, 01:46

nitishmahajan wrote:

target2011 wrote:

hello guys, i do not know where to post this problem so i am posting it here.

Laura has 20 coins consisting of quarters and dimes. If she has a total of $3.05, how many dimes does she have?

a. 3 b. 7 c. 10 d. 13 e. 16

i was struggling for more than half an hour but cudn't get the answer, finally i tried with all options and got the correct answer. pls guide.

Lets assume Laura has X quarters and Y dimes, then we know X+Y=20 and also 0.25X + 0.1Y = 3.05

solve these and you will get the answer

Another way of looking at it ..!

We know that sum is $3.05 which means number of quarters or dimes will odd, so straight away u can eliminate the even answer options ( 10 and 16 ) now we are left with options 3, 7 and 13, clearly in the left options you can clearly see that 13 can be the only candidate.

Or you can also use the spilt option to make it easy by plugging in use 10 first and you will see that answer has to be greater than 10 ..

hey, thanks.

pls throw a little light on We know that sum is $3.05 which means number of quarters or dimes will odd i didn't understood this.

and dude, can u pls tell me which is the best book for GMAT Quants? _________________

"Great people don't do different things, they do things differently"

Re: GMAT Prep few more [#permalink]
23 Feb 2010, 09:29

target2011 wrote:

nitishmahajan wrote:

target2011 wrote:

hello guys, i do not know where to post this problem so i am posting it here.

Laura has 20 coins consisting of quarters and dimes. If she has a total of $3.05, how many dimes does she have?

a. 3 b. 7 c. 10 d. 13 e. 16

i was struggling for more than half an hour but cudn't get the answer, finally i tried with all options and got the correct answer. pls guide.

Lets assume Laura has X quarters and Y dimes, then we know X+Y=20 and also 0.25X + 0.1Y = 3.05

solve these and you will get the answer

Another way of looking at it ..!

We know that sum is $3.05 which means number of quarters or dimes will odd, so straight away u can eliminate the even answer options ( 10 and 16 ) now we are left with options 3, 7 and 13, clearly in the left options you can clearly see that 13 can be the only candidate.

Or you can also use the spilt option to make it easy by plugging in use 10 first and you will see that answer has to be greater than 10 ..

hey, thanks.

pls throw a little light on We know that sum is $3.05 which means number of quarters or dimes will odd i didn't understood this.

and dude, can u pls tell me which is the best book for GMAT Quants?

Question says $ 3.05 is the sum of the quarters and dimes, and total number of coins =20

Now, we know dime = 0.10 and quarter =0.25, and say for e,g number of quarters is even ( For eg 10) then the total value of 10 quarters would be $ 2.50 and also dime value is $ 0.1 , so irrespective of the fact that whether number of dimes is even or odd the sum of the dime value will be a multiple of 10

So to have the total of $3.05 ( or I should say .05 Cents, the number of quarters will be odd like 3, 7, 9, etc)

Hope that helps..!

About the book, I am not an expert but I guess if you read a couple of posts by experts on their strategy and GMAT journey, you will find pretty nice books.

In fact you can also read the initial threads in the maths forum where moderators have compiled the list of all the good books ..!

gmatclubot

Re: GMAT Prep few more
[#permalink]
23 Feb 2010, 09:29