Question

for an AP if t1=5 tn =45,Sn=125 find n​

Answer 1

Answer:

in AP there is a general formula for sum

sum = n/2(first term + last term)

sum = 125

t1 = 5

tn = 45

125 = n/2(5+45)

125 = 25n/2

n = 10

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Answer 2

Answer:

5

Step-by-step explanation:

so sn = n/2*(a+l)

125 =n/2*50

n=125/25=5