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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, 00:35
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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

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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, 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
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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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New post 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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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, 07:15
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


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Joined: 06 Jan 2015
Posts: 529
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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, 07:37
chetan2u This sounds good thanks a lot now I got it.
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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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