5. (ii) Find the number of terms in the A.P: 18, 15.5, 13,......., - 47.
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Answer:
number of terms = 25
Step-by-step explanation:
given : a = 18, d = 15.5 - 18 = -2.5, L = Tn = -47
to find number of terms n
formula used Tn = a + (n-1)d
- 47 = 18 + (n -1) × -2.5
-47 = 18 - 2.5 n + 2.5
=> - 47 - 18 - 2.5 = -2.5 n
=> -67.5 = - 2.5 n
=> n = -67.5/-2.5
=> n = 25
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