The first and last term of an ap are 5 and 45 respectively if the sum of all its terms is 400 find in common difference
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Answered by
84
a= 5 ,an=45
Sn=n/2 (a+l)
400=n/2 (5+45)
400=n/2×50
400=25n
n=16
an=a+(n-1)d
45=5+(16-1)d
45-5=(16-1)d
40=(16-1)d
40=15d
d=8/3
Sn=n/2 (a+l)
400=n/2 (5+45)
400=n/2×50
400=25n
n=16
an=a+(n-1)d
45=5+(16-1)d
45-5=(16-1)d
40=(16-1)d
40=15d
d=8/3
Answered by
12
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