Find 25th term of an ap where 11th term is 38 and 16 is 73
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Answer:
136
Step-by-step explanation:
t11=38, n=11
tn=a+(n-1)×d
t11=a+(11-1)×d
38=a+10d
a+10d=38----------------(1)
t16=73, n=16
tn=a+(n-1)×d
t16=a+(16-1)×d
73=a+15d
a+15d=73----------------(2)
subtracting eqn(1) from (2)
a+15d=73
— a+10d=38
--------------------
5d=35
d=35/5
d=7
substituting d=7 in eqn (1)
a+10d=38
a+10×7=38
a+70=38
a =38-70
a=-32
now, a=-32, d=7, n=25, t25=?
tn=a+(n-1)×d
t25=-32+(25-1)×7
=-32+24×7
=-32+168
t25=136
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