sum of 2 digit multiples of 7 which are not multiple of 3 is divided by 13 .Find the remainder
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16
10 to 99
the no. exactly divisibe by 7
14,21,28……98.
the no. which leaves reminder of 3.
add 3 to each no. which are exactly divisible by 7
10,17,24,31…94
(7+3=10 two digit, 98+3=101 not a 2digit no.)
this is a A.P. a=10,d=7
an=a+(n-1)d
94=10+(n-1)7
n=13
sn = n/2(a+l)10 to 99
the no. exactly divisibe by 7
14,21,28……98.
the no. which leaves reminder of 3.
add 3 to each no. which are exactly divisible by 7
10,17,24,31…94
(7+3=10 two digit, 98+3=101 not a 2digit no.)
this is a A.P. a=10,d=7
an=a+(n-1)d
94=10+(n-1)7
n=13
sn = n/2(a+l)
=13/2(10+94)
676
=13/2(10+94)
676
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7
very good answer.but I don't know amswer
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