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PostPosted: Tue Jun 22, 2021 1:41 pm 
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Joined: Thu Mar 13, 2014 1:38 pm
Posts: 16
Hi,
Need help in solving these please (along with the steps/method of solving please):

1)Arya rings every multiple of 13 less than 500. She then crosses every multiple of 17 less than 500. How many numbers get ringed and crossed.

options are: 10 / 0 /1 /2/ 4

2) Eve adds together the number from the first throw and the number from the second dice she throws. What is the mot likely total she can expect?

options are 7/ 8 / 6 / 9 / 10

Thanks.


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PostPosted: Tue Jun 22, 2021 4:43 pm 
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Joined: Fri Sep 15, 2006 9:51 am
Posts: 10082
I am no mathematician so I might be missing the point (hope someone points out if there is another answer) but what I would do would be:

1) I assume that as 13 and 17 are both prime numbers there wouldn't be any lower factors to worry about so it would be a case of :

13*17=221 so 221 would be ringed and crossed

then 13*17*2 = 442 would be also crossed & ringed

the next number would be over 500 - so the number of instances would be (2)

2) what is the commonest total from two dice?

this is case of how many ways any of the numbers can be made up - so

2=1+1
3=1+2 or 2+1
4=1+3 or 2+2 or 3+1
5=1+4 or 2+3 or 4+1 or 3+2

etc so then check how many ways there are to get 6,7,8,9,10


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PostPosted: Tue Jun 22, 2021 6:46 pm 
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Joined: Mon Jun 18, 2007 3:32 pm
Posts: 7698
Location: East Kent
Iā€™m with Hermie on this one.
ā€œ13 and 17ā€ jump out.

Learning times tables, especially factors primes, squares and cubes is a short cut to lots of 11+ times questions


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PostPosted: Mon Jul 05, 2021 1:02 pm 
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Joined: Thu Mar 13, 2014 1:38 pm
Posts: 16
Thanks Hermanmunster and YoYo for the explanation. Apologies for the late reply.


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