The three digits of a number add to 11.

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rakeshd347: Master | Next Rank: 500 Posts; Posts: 391; Joined: Sat Mar 02, 2013 5:13 amFollowed by: 4 members; Thanked: 50 times

by rakeshd347 » Tue Oct 08, 2013 8:58 pm

The three digits of a number add to 11. The number is completely divisible by 5. The first digit is double of the second digit. What is the product of the three digits?

a) 27
b) 36
c) 39
d) 40
e) 63

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theCodeToGMAT: Legendary Member; Posts: 1556; Joined: Tue Aug 14, 2012 11:18 pmFollowed by: 34 members; Thanked: 448 times; GMAT Score:650

by theCodeToGMAT » Tue Oct 08, 2013 9:02 pm

A B C

C = 5 or 0

Since, the question says product of digits and none of answer choices has product = 0 so "5" is possible

B = a
A = 2a

a + 2a = 11 - 5
3a = 6
a = 2
hence number 425
product = 40
Answer [spoiler]{D}[/spoiler]

R A H U L

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[email protected]: Elite Legendary Member; Posts: 10392; Joined: Sun Jun 23, 2013 6:38 pmFollowed by: 511 members; Location: Palo Alto, CA; Thanked: 2867 times; GMAT Score:800

by [email protected] » Tue Oct 08, 2013 10:16 pm

Hi rakeshd347,

When a question has a limited number of possibilities, you can sometimes "brute-force" your way to the solution. You WILL have to do work though; staring is NOT an option.

Here, we have a bunch of facts to work with:
1) A 3-digit number
2) Digits add up to 11
3) Number is evenly divisible by 5 (so it ends in 0 or 5)
4) The first digit is double the second digit.

Starting with the last fact, we only have a four options:
21_
42_
63_
84_

If you plug 0 in for the last digit, you WON'T end up with a sum of 11, so the last digit MUST be a 5 and the only possible 3-digt number is...

425

Now, answer the question...

Final Answer: D

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]

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rakeshd347: Master | Next Rank: 500 Posts; Posts: 391; Joined: Sat Mar 02, 2013 5:13 amFollowed by: 4 members; Thanked: 50 times

by rakeshd347 » Tue Oct 08, 2013 11:15 pm

rakeshd347 wrote:The three digits of a number add to 11. The number is completely divisible by 5. The first digit is double of the second digit. What is the product of the three digits?

a) 27
b) 36
c) 39
d) 40
e) 63

I was looking for the more logical answer for this without picking up pen and paper and I thought of it myself.
Now the unit digit has to be either 5 or 0 as it is divisible by 5. If it were 0, then the product of the three digits will be 0 right. But no answer choice gives 0 as the option so obviously it has to be 5. Now the product has to be divisible by 5 as well and the only choice divisible by 5 is D.
Without pen and paper

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theCodeToGMAT: Legendary Member; Posts: 1556; Joined: Tue Aug 14, 2012 11:18 pmFollowed by: 34 members; Thanked: 448 times; GMAT Score:650

by theCodeToGMAT » Tue Oct 08, 2013 11:19 pm

rakeshd347 wrote:
rakeshd347 wrote:The three digits of a number add to 11. The number is completely divisible by 5. The first digit is double of the second digit. What is the product of the three digits?

a) 27
b) 36
c) 39
d) 40
e) 63
I was looking for the more logical answer for this without picking up pen and paper and I thought of it myself.
Now the unit digit has to be either 5 or 0 as it is divisible by 5. If it were 0, then the product of the three digits will be 0 right. But no answer choice gives 0 as the option so obviously it has to be 5. Now the product has to be divisible by 5 as well and the only choice divisible by 5 is D.
Without pen and paper

Even the solution i gave, i solved without pen and paper

...

But, i took & followed Ron's advise, which he gave yesterday; We are not the only one who is reading this forum.. and we should post "sound" solutions

R A H U L

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rakeshd347: Master | Next Rank: 500 Posts; Posts: 391; Joined: Sat Mar 02, 2013 5:13 amFollowed by: 4 members; Thanked: 50 times

by rakeshd347 » Tue Oct 08, 2013 11:29 pm

theCodeToGMAT wrote:
rakeshd347 wrote:
rakeshd347 wrote:The three digits of a number add to 11. The number is completely divisible by 5. The first digit is double of the second digit. What is the product of the three digits?

a) 27
b) 36
c) 39
d) 40
e) 63
I was looking for the more logical answer for this without picking up pen and paper and I thought of it myself.
Now the unit digit has to be either 5 or 0 as it is divisible by 5. If it were 0, then the product of the three digits will be 0 right. But no answer choice gives 0 as the option so obviously it has to be 5. Now the product has to be divisible by 5 as well and the only choice divisible by 5 is D.

No don't take me wrong. Yours and Rich's solution is great and it can be done in less than a minute actually but now a days I am getting my brain used to of thinking logically and answer questions.
Honestly in the first attempt I solved the same way as you solved it

Thanks
Without pen and paper
Even the solution i gave, i solved without pen and paper ...

But, i took & followed Ron's advise, which he gave yesterday; We are not the only one who is reading this forum.. and we should post "sound" solutions

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GMAT/MBA Expert

[email protected]: Elite Legendary Member; Posts: 10392; Joined: Sun Jun 23, 2013 6:38 pmFollowed by: 511 members; Location: Palo Alto, CA; Thanked: 2867 times; GMAT Score:800

by [email protected] » Wed Oct 09, 2013 10:25 am

Hi rakeshd347,

Based on what you just wrote, I thought that I would add a word of warning:

Just about every silly mistake that you'll make on this test will be because you DID NOT write anything down. Doing work "in your head" will kill you on the GMAT.

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]

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ganeshrkamath: Master | Next Rank: 500 Posts; Posts: 283; Joined: Sun Jun 23, 2013 11:56 pmFollowed by: 26 members; Location: Bangalore, India; Thanked: 97 times; GMAT Score:750

by ganeshrkamath » Thu Oct 10, 2013 1:04 am

rakeshd347 wrote:The three digits of a number add to 11. The number is completely divisible by 5. The first digit is double of the second digit. What is the product of the three digits?

a) 27
b) 36
c) 39
d) 40
e) 63

Let the number be abc
a+b+c=11
c can be either 0 or 5.
If c = 0 => a*b*c = 0
This is not in the options.

So c = 5
Product = a*b*c = 5ab
So the product is also a multiple of 5.
Choose d

Cheers

Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Kelley School of Business (Class of 2016)
GMAT Score: 750 V40 Q51 AWA 5 IR 8
https://www.beatthegmat.com/first-attemp ... tml#688494

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