Question

IN AN AP, IF a=5 , d=2.5 , an= 10 then value of 'n' is?

Answer 1

an=a+(n-1)d
10=5+2.5n-2.5
10=2.5+2.5n
10=5/2(n+1)
4=n+1
n=3
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Answer 2

a+(n-1) d=10 5+(n-1) 2.5=10 n-1=5÷2.5 n=2+1=3