If S10 = 55 and S9 = 45 find a10
Answers
Answered by
7
Step-by-step explanation:
Sn=n/2{2a+(n-1)d}
S10=10/2{2a+9d}
55=5{2a+9d}
11=2a+9d----------1
S9=9/2{2a+8d}
45x2=9{2a+8d}
10=2a+8d-----------2
eqn1 - eqn2
d=1
put the value of d in eqn1
a=1
t10=1+9x1
=1+9
=10
Answered by
3
Given:
S10 = 55 and S9 = 45
To Find:
a10
Solution:
Sn = n/2{2a+(n-1)d}
S10 = 10/2{2a+9d}
55 = 5{2a+9d}
11 = 2a + 9d ----------(1)
S9 = 9 / 2{2a+8d}
45x2 = 9{2a+8d}
10 = 2a + 8d -----------(2)
On subtracting (2) from (1), we get
d=1
Putting the value of d in (1) , we get
a=1
t10 = 1 + 9x1
= 1 + 9
= 10
Hence, a10 = 10.
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