Question

Find the number of terms in the A.P. : 18,15*1/2,13,....,-47​

Answer 1

Answer:

Step-by-step explanation:

a= 18

l = -47

d = -21/2

n = ?

l = a + (n-1).d

-47 = 18 - 21n/2 + 21/2. ( -*- = +)

Taking L.C.M.

-47 = ( 36 - 21n +21 )/2

taking 2 on L.H.S.

-94 = 57 - 21n

taking 57 on L.H.S.

-94 -57 = -21n

-151 = -21n

151 = 21n ( - sign will get cancelled on both the sides)

n = 151/21

n = 7.1904

therefore, n = 7. (ignoring decimal numbers)

THEREFORE OUR FINAL ANSWER IS n = 7

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