the sum of 5 th and 16 th term of an arithmetic sequence is 67. if the 10 th term is 32 what is it's 11 th term
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Answer:
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Step-by-step explanation:
so for the above ap we need to find t11 i.e. its 11th term
now let the 5th term of an AP be a+4d and 16th term be a+15d
so according to first condition
a+4d+a+15d=67
ie 2a+19d=67 (1)
so for second condition
we have to use formula
tn=a+(n-1)d
so according to second condition
t10=32
put n=10 in above formula
we get t10=a+(10-1)d
ie a+9d=32 (2)
so multiply (2) by 2
we get 2a+18d=64 (3)
subtract (3) from (2)
we get
2a+19d=67
2a+18d=64
(-) (-) (-)
__________
d=3
so d=3
substitute value of d in any of three equations
we get a=5
so now again using
tn=a+(n-1)d
but put n=11
we get t11=5+[(11-1)×3]
=5+(10×3)
=30+5
so t11=35
hence 11th term of above ap is 35