AQUiLA MAGAZINE
MEGAMATHS
Print out the grid attached and then do the following :
STEP 1 : First , cross out or shade in all numbers that are multiples of 2 , except for 2 itself ( 2 is the only even prime
number ).
STEP 2 : Then cross out or shade multiples of 3 , except 3 itself . Some of these numbers might already be crossed out , where a number can be divided by 2 and 3 .
STEP 3 : You would then cross out or shade multiples of 4 , except you ’ ve already done these when you did multiples of 2 ( as 4 is a multiple of 2 , and any multiple of 4 is also a multiple of 2 ).
STEP 4 : So , next cross out or shade multiples of 5 , except 5 itself . Again , some numbers will already be done from previous sifts of the sieve .
STEP 5 : There ’ s no need to do multiples of 6 , as 6 is the same as 2 x 3 , so the sifts for 2 and 3 would have covered all these . So , move on to multiples of 7 , leaving 7 itself .
STEP 6 : You can ignore sifts for 8 , 9 and 10 – why ?
Your sieve is also complete at this stage . All numbers showing as not shaded / not crossed out are prime numbers .
CALCULATA WANTS TO HEAR HOW YOU GOT ON !
Why not let us know via the usual address on the AQUILAnauts ’ page of the AQUILA website .
www . aquila . co . uk / aquilanauts
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© AQUILA Magazine . Written by Iqbal Hussain
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