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

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Manager
Joined: 07 Jun 2017
Posts: 176

Kudos [?]: 90 [0], given: 59

Location: India
Concentration: Technology, General Management
GMAT 1: 660 Q46 V38
GPA: 3.6
WE: Information Technology (Computer Software)
What are the last two digits (at ten's place and unit’s place) in the [#permalink]

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24 Oct 2017, 01:35
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Difficulty:

95% (hard)

Question Stats:

21% (01:06) correct 79% (01:02) wrong based on 39 sessions

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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

Math Expert
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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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24 Oct 2017, 06:54
Expert's post
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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
_________________

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

Manager
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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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?
_________________

आत्मनॊ मोक्षार्थम् जगद्धिताय च

Resource: GMATPrep RCs With Solution

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

Math Expert
Joined: 02 Aug 2009
Posts: 5227

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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24 Oct 2017, 08:15
1
KUDOS
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
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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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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# What are the last two digits (at ten's place and unit’s place) in the

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