Question

Complete the activity to find out the number of terms in an A.P 1, 3, 5, .....149.
Here a=1, d= 0 , tn = 149
tn = a + (n - 1)d
... 149 = 0
.. 149 = 2n-
in=7
​

Answer 1

a = 1

d = 3 - 1 = 2

tn = 149

Formula

tn = a + ( n - 1)d

149 = 1 + (n - 1)2

148 = (n - 1) 2

n = 75

Answer 2

here : a = 1 , d = a2-a1 = 3-1 =2 , an = 149

an = a + ( n - 1 ) × d

149 = 1 + ( n - 1 ) × 2

149 = 1 + 2n - 2

149 = 1 + 2n

149-1 = 2n

148 = 2n

148 / 2 = n

74 = n