find the sum of all number from 1 to 350 which are divisible by 6 hence find the 15th term of an A.P
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6,12,18..........348
an=a+(n-1)d
348=6+(n-1)6
348-6=(n-1)6
342=(n-1)6
342÷6=(n-1)
48=(n-1)
48+1=n
49=n
Sn= n/2[2a+(n-1)d]
=49/2[2×6+(49-1)6]
=49/2[12+(48)6]
=49/2[12+288]
=49/2[300]
=49×150
=7350
a15=6+(15-1)6
=6+14×6
=6+84
=90
an=a+(n-1)d
348=6+(n-1)6
348-6=(n-1)6
342=(n-1)6
342÷6=(n-1)
48=(n-1)
48+1=n
49=n
Sn= n/2[2a+(n-1)d]
=49/2[2×6+(49-1)6]
=49/2[12+(48)6]
=49/2[12+288]
=49/2[300]
=49×150
=7350
a15=6+(15-1)6
=6+14×6
=6+84
=90
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