Goi so hs khoi 6 cua truong do la a ( hs ) ,a
thuoc N*
Ta co a÷4,5,6,10 thua 2 , a chia het cho 7va a<260. Vi a÷4,5,6,10 thua 2
=>a-2 chia het 4,5,6,10
=>a-2 thuoc BC(4,5,6,10)
4=2^2
5=5
6=2.3
10=2.5
BCNN(4,5,6,10)=2^2 . 3 . 5 = 60
BC(4,5,6,10)=B(60)={0,60,120,180,240,300,....}
=>a-2thuoc{0,60,120,180,240,300,...}
=>a thuoc {2,62,122,182,242,302,...}
Ma a <260 va chia het cho 7nen a=182
Vay so hs khoi 6 cua truong do la 182 hs