Find the sum of all natural numbers b/w 200 and 1502 which are exactly

1.	Find the sum of all natural numbers b/w 200 and 1502 which are exactly divisible by 3
Answer» The AP is 201,204,207,......1500a=201 d= 3 l=1500Sn= a+(n-1)d1500= 201+(n-1)31500=201+3n-33n=1500-1983n=1302n=1302/3n=434Sn=N/2(a+l)a=201l=1500n=434Sn = 434/2 (201 + 15000Sn = 217 (1701)Sn = 369117Therefore Sn=369117

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