Let an be an arithmetic progression, for which a3=13 and a11=25a11=25. Find a7
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See the answer in the attachment !
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See the answer in the attachment !
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Hi ,
Let a and d are first term and common
difference of an A.P
nth term = an
an = a + ( n - 1 ) d
according to the problem given,
a3 = 13
a + ( 3 - 1 )d= 13
a + 2d = 13 ---( 1 )
a11 = 25
a + ( 11 - 1 ) d = 25
a + 10d = 25 ---( 2 )
subtract ( 1 ) from ( 2 ) , we get
8d = 12
d = 12 / 8
d = 3/ 2
put d = 3/2 in ( 1 )
a + 2× ( 3/2 ) = 13
a + 3 = 13
a = 13 - 3
a = 10
Therefore ,
a = 10 , d = 3/2
a7 = a + ( 7 - 1 ) d
= a + 6d
= 10 + 6 × ( 3/2 )
= 10 + 9
a7 = 19
I hope this helps you.
:)
Let a and d are first term and common
difference of an A.P
nth term = an
an = a + ( n - 1 ) d
according to the problem given,
a3 = 13
a + ( 3 - 1 )d= 13
a + 2d = 13 ---( 1 )
a11 = 25
a + ( 11 - 1 ) d = 25
a + 10d = 25 ---( 2 )
subtract ( 1 ) from ( 2 ) , we get
8d = 12
d = 12 / 8
d = 3/ 2
put d = 3/2 in ( 1 )
a + 2× ( 3/2 ) = 13
a + 3 = 13
a = 13 - 3
a = 10
Therefore ,
a = 10 , d = 3/2
a7 = a + ( 7 - 1 ) d
= a + 6d
= 10 + 6 × ( 3/2 )
= 10 + 9
a7 = 19
I hope this helps you.
:)
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