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What are the last two digits (at ten's place and unit’s place) in the

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What are the last two digits (at ten's place and unit’s place) in the [#permalink]

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New post 24 Oct 2017, 01:35
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What are the last two digits (at ten's place and unit’s place) in the numerical value of the following product?

243 x 5787 x 5315 x 7779 x 8262 x 3179 x 993.

A. 10
B. 30
C. 50
D. 70
E. 90
[Reveal] Spoiler: OA

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email: nkmungila@gmail.com
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Kudos [?]: 90 [0], given: 59

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What are the last two digits (at ten's place and unit’s place) in the [#permalink]

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New post 24 Oct 2017, 06:54
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nkmungila wrote:
What are the last two digits (at ten's place and unit’s place) in the numerical value of the following product?

243 x 5787 x 5315 x 7779 x 8262 x 3179 x 993.

A. 10
B. 30
C. 50
D. 70
E. 90



hi..

we have numbers with 2 and 5, so UNIT's place is surely 0..
here we have to find the tens digit too..

this will be given by \(5315*8262..... 15*2=30\)

rest all numbers we require to concentrate on only the UNITs digit
\(243 * 5787 * 7779 * 3179 * 993.......3*7*9*9*3....21*81*3......1*1*3=3\)

so LAST two digits are 30*3=90

E
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Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

Kudos [?]: 5876 [0], given: 118

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Re: What are the last two digits (at ten's place and unit’s place) in the [#permalink]

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New post 24 Oct 2017, 07:36
chetan2u wrote:
nkmungila wrote:
What are the last two digits (at ten's place and unit’s place) in the numerical value of the following product?

243 x 5787 x 5315 x 7779 x 8262 x 3179 x 993.

A. 10
B. 30
C. 50
D. 70
E. 90



hi..

we have numbers with 2 and 5, so UNIT's place is surely 0..
here we have to find the tens digit too..

this will be given by \(5315*8262..... 15*2=30\)

rest all numbers we require to concentrate on only the UNITs digit
\(243 * 5787 * 7779 * 3179 * 993.......3*7*9*9*3....21*81*3......1*1*3=3\)

so LAST two digits are 30*3=90

E


HI chetan2u

Can you please explain why are we multiplying 30*3 here?

Is it not we just multiply 3*7*9*9*3*10?
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आत्मनॊ मोक्षार्थम् जगद्धिताय च

Resource: GMATPrep RCs With Solution

Kudos [?]: 111 [0], given: 469

Expert Post
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Math Expert
User avatar
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Joined: 02 Aug 2009
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Kudos [?]: 5876 [1], given: 118

What are the last two digits (at ten's place and unit’s place) in the [#permalink]

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New post 24 Oct 2017, 08:15
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Expert's post
NandishSS wrote:
chetan2u wrote:
nkmungila wrote:
What are the last two digits (at ten's place and unit’s place) in the numerical value of the following product?

243 x 5787 x 5315 x 7779 x 8262 x 3179 x 993.

A. 10
B. 30
C. 50
D. 70
E. 90



hi..

we have numbers with 2 and 5, so UNIT's place is surely 0..
here we have to find the tens digit too..

this will be given by \(5315*8262..... 15*2=30\)

rest all numbers we require to concentrate on only the UNITs digit
\(243 * 5787 * 7779 * 3179 * 993.......3*7*9*9*3....21*81*3......1*1*3=3\)

so LAST two digits are 30*3=90

E


HI chetan2u

Can you please explain why are we multiplying 30*3 here?

Is it not we just multiply 3*7*9*9*3*10?


Hi..
2 and 5 give us the last digit 0, and th esecond last will be given by the remaining last digit incl the second last of terms giving 0..

LOOK it this way..

\(243 * 5787 * 5315 * 7779 * 8262 * 3179 * 993 = 243 * 5787 * \frac{5315}{5} * 5 * 7779 * \frac{8262}{2} * 2 * 3179 * 993 =243 * 5787 * 1063 * 7779 * 4131 * 3179 * 993 *10\)...
now take units digit... \(3*7*3*9*1*9*3*10=90\)
_________________

Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

Kudos [?]: 5876 [1], given: 118

Manager
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avatar
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Joined: 06 Jan 2015
Posts: 237

Kudos [?]: 111 [0], given: 469

Location: India
Concentration: Operations, Finance
GPA: 3.35
WE: Information Technology (Computer Software)
Re: What are the last two digits (at ten's place and unit’s place) in the [#permalink]

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New post 24 Oct 2017, 08:37
chetan2u This sounds good thanks a lot now I got it.
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Resource: GMATPrep RCs With Solution

Kudos [?]: 111 [0], given: 469

Re: What are the last two digits (at ten's place and unit’s place) in the   [#permalink] 24 Oct 2017, 08:37
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