the first term of an AP is 5; the last term is45 and the sum of all its terms is 400 find the number of terms and the common difference of the AP
Answers
Answered by
3
Step-by-step explanation:
a=5, an=45, Sn=400,n=?
Sn=n/2(a+an)
=> 400=n/2(5+45)
400*2/50=n
16=n.
Answered by
2
Given:
a = 5
an = 45
sn = 400
sn = (n/2)*(a + an)
400 = (n/2)*(5 + 45)
800 = n*50
n = 800/50 = 16
an = a + (n - 1)*d
45 = 5 + (16 - 1)*d
40 = 15 * d
d = 40/15 = 8/3
n = 16, d = 8/3 ——> Answer
a = 5
an = 45
sn = 400
sn = (n/2)*(a + an)
400 = (n/2)*(5 + 45)
800 = n*50
n = 800/50 = 16
an = a + (n - 1)*d
45 = 5 + (16 - 1)*d
40 = 15 * d
d = 40/15 = 8/3
n = 16, d = 8/3 ——> Answer
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