Question

in an ap the first term is 2 the last term is 20 and the sum of the terms is 165 find the common difference of the ap

Answer 1

Step-by-step explanation:

given:

a=2

lth term=20

sum=165

sum of l terms=l/2*(2a+(l-1) d) .......i

so first we need to find l

lth term=a+(l-1)d

20=2+(l-1) d.........ii

therefore,

18=(l-1) d........ iii

substituting value of i in iii

165=l/2*(2a+18)

165=l/2*(4+18)

165=l/2*22

165=11l

l=15.......iv

substituting value of iv in ii

20=2+14d

18=14d

d=18/14

d=9/7......ans

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