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Re: Whats the reminder when 42,527,152,653,425,416,242,624,272,427,215,287 [#permalink]
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I tried the following approach:

42527152653425416242624272427215287/16 = 42527152653425416242624272427215280/16 + 7/16

Now the last two digits of first term, 80 is divisible by 4 and so is the denominator 16.

Again, 80/16 = 20/4 also divides , so remainder = 7

Answer - B

But I'm not 100% convinced with my approach.
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Re: Whats the reminder when 42,527,152,653,425,416,242,624,272,427,215,287 [#permalink]
subhashghosh wrote:
I tried the following approach:

42527152653425416242624272427215287/16 = 42527152653425416242624272427215280/16 + 7/16

Now the last two digits of first term, 80 is divisible by 4 and so is the denominator 16.

Again, 80/16 = 20/4 also divides , so remainder = 7

Answer - B

But I'm not 100% convinced with my approach.


Hi Subhash, even i doubt your approach.. I tried randomly sum numbers using ur approach, but it doesnt work..

https://staff.argyll.epsb.ca/jreed/math7 ... 1/1104.htm
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Re: Whats the reminder when 42,527,152,653,425,416,242,624,272,427,215,287 [#permalink]
Yup.. I'll wait for experts to opine on this.
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Re: Whats the reminder when 42,527,152,653,425,416,242,624,272,427,215,287 [#permalink]
sudhir18n wrote:
dimri10 wrote:
whats the reminder when 42527152653425416242624272427215287 is dividd by 16

a.1
b.7.
c.2.
d.3
e.9


divisibility by 16 .. take last 4 digits
5287 mod 16 = 7
hence B

it seems like a wise mehod.kudos
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Re: Whats the reminder when 42,527,152,653,425,416,242,624,272,427,215,287 [#permalink]
@sudhir18n

even though your approach worked here , i dont think it can be generalized that way. It may not yield the right answer all the time.

eg : 2782 when divided by 16 leaves a remainder of 6

but 12782 when divided by 16 leaves a remainder of 14

so if we you get 12782 and were asked to find remainder when divided by 16
if you go by 4 digit approach then that would be wrong..



sudhir18n wrote:
dimri10 wrote:
whats the reminder when 42527152653425416242624272427215287 is dividd by 16

a.1
b.7.
c.2.
d.3
e.9


divisibility by 16 .. take last 4 digits
5287 mod 16 = 7
hence B
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Re: Whats the reminder when 42,527,152,653,425,416,242,624,272,427,215,287 [#permalink]
Spidy001 wrote:
@sudhir18n

even though your approach worked here , i dont think it can be generalized that way. It may not yield the right answer all the time.

eg : 2782 when divided by 16 leaves a remainder of 6

but 12782 when divided by 16 leaves a remainder of 14

so if we you get 12782 and were asked to find remainder when divided by 16
if you go by 4 digit approach then that would be wrong..

sudhir18n wrote:
dimri10 wrote:
whats the reminder when 42527152653425416242624272427215287 is dividd by 16

a.1
b.7.
c.2.
d.3
e.9


divisibility by 16 .. take last 4 digits
5287 mod 16 = 7
hence B



are you sure 2782 mod 16 = 6
im getting 14 ..
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Re: Whats the reminder when 42,527,152,653,425,416,242,624,272,427,215,287 [#permalink]
Yeah u r right. I mis calculated that one .

Posted from my mobile device
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Re: Whats the reminder when 42,527,152,653,425,416,242,624,272,427,215,287 [#permalink]
Can someone pls explain what the approach should be for such a question
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Re: Whats the reminder when 42,527,152,653,425,416,242,624,272,427,215,287 [#permalink]
We all know 100 is divisible by 4 so 100x100 is divisible by 4x4. To find the remainder of A divided by 16, we just need the last 4 digits.
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Re: Whats the reminder when 42,527,152,653,425,416,242,624,272,427,215,287 [#permalink]
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16 is a multiple of 8 and 2. A number can be checked for 8, by dividing the last 3 digits and for 2 by dividing the last digit. Here 287 will result in 7 as a remainder when divided by 8 and 1 when divided by 2. Therefore the remainder is 7*1 = 7.
Break down the divisor into smaller factors and perform the division check.




dimri10 wrote:
Whats the reminder when 42,527,152,653,425,416,242,624,272,427,215,287 is divided by 16

A. 1
B. 7.
C. 2.
D. 3
E. 9
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Re: Whats the reminder when 42,527,152,653,425,416,242,624,272,427,215,287 [#permalink]
can we follow this approach every time ? for last 2,3,4 digits and check the divisibility test ?
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Re: Whats the reminder when 42,527,152,653,425,416,242,624,272,427,215,287 [#permalink]
Amit0507 wrote:
16 is a multiple of 8 and 2. A number can be checked for 8, by dividing the last 3 digits and for 2 by dividing the last digit. Here 287 will result in 7 as a remainder when divided by 8 and 1 when divided by 2. Therefore the remainder is 7*1 = 7.
Break down the divisor into smaller factors and perform the division check.




dimri10 wrote:
Whats the reminder when 42,527,152,653,425,416,242,624,272,427,215,287 is divided by 16

A. 1
B. 7.
C. 2.
D. 3
E. 9



I used the same approach of 287 div by 8 gives remainder as 7. Now I divided 7 by 2 to get remainder as 1. So my Answer was A, which i now know is wrong. But I dont understand your last step of multiplying 7*1 = 7 as remainder. What's your thought process doing that step ? Any help appreciated.
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Re: Whats the reminder when 42,527,152,653,425,416,242,624,272,427,215,287 [#permalink]
Amit0507 wrote:
16 is a multiple of 8 and 2. A number can be checked for 8, by dividing the last 3 digits and for 2 by dividing the last digit. Here 287 will result in 7 as a remainder when divided by 8 and 1 when divided by 2. Therefore the remainder is 7*1 = 7.
Break down the divisor into smaller factors and perform the division check.




dimri10 wrote:
Whats the reminder when 42,527,152,653,425,416,242,624,272,427,215,287 is divided by 16

A. 1
B. 7.
C. 2.
D. 3
E. 9


Used exactly this approach.

took out remainders with both 2 and 8 and then multiplied by them
and lastly ensure the product < 16
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Re: Whats the reminder when 42,527,152,653,425,416,242,624,272,427,215,287 [#permalink]
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