5. The first term of an AP is 5. the last term is 45 and the sum is 400. Find the number of term sare the common difference.
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Answer:
Step-by-step explanation:
a = 5
an = 45
Sn = 400
Sn = n/2(a + l) where l is the last term
400 = n/2(5+45)
50n/2 =400
50n =800
n = 800/50
n = 16
No of terms = 16
an = a +(n-1).d
45 = 5 + (16-1)d
45-5 = 15d
d = 40/15
=8/3
Common difference = 8/3
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