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

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Joined: 07 Jun 2017
Posts: 174
Location: India
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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, 00:35
1
3
00:00

Difficulty:

95% (hard)

Question Stats:

29% (02:05) correct 71% (01:41) wrong based on 54 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

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email: nkmungila@gmail.com
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Joined: 02 Aug 2009
Posts: 7107
What are the last two digits (at ten's place and unit’s place) in the  [#permalink]

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24 Oct 2017, 05:54
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
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

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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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24 Oct 2017, 06:36
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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Math Expert
Joined: 02 Aug 2009
Posts: 7107
What are the last two digits (at ten's place and unit’s place) in the  [#permalink]

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24 Oct 2017, 07:15
1
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... $$3*7*3*9*1*9*3*10=90$$
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

GMAT online Tutor

Director
Joined: 06 Jan 2015
Posts: 529
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, 07:37
chetan2u This sounds good thanks a lot now I got it.
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Resource: GMATPrep RCs With Solution

Re: What are the last two digits (at ten's place and unit’s place) in the &nbs [#permalink] 24 Oct 2017, 07:37
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