Question

find the 12 term from the end of ap 7,11,15,....139​

Answer 1

Answer:

95

Step-by-step explanation:

we take the AP in reverse order as 12th term from end is required.

the series becomes 139, 135, 131......... 7.

a = 139 d = -4 n = 12

an = a + (n-1)d

= 139 + (12-1)(-4)

= 139 + (11× -4)

= 139 + (-44)

= 139 - 44

= 95

therefore the 12th term from end of AP 7, 11, 15 ..... 139 is 95

method 2

a = 7 d = 4 an = 139 n = ?

an = a + (n - 1) d

139 = 7 + (n - 1) (4)

139 - 7 = (n - 1) (4)

132 = (n - 1)(4)

n - 1 = 132/4

n - 1 = 33

n = 33 + 1

n = 34

12th term from end Will be = number of terms - (12 - 1)

34 - (12 -1) = 34 - 11 = 23

we need to find n = 2

an = a + (n - 1) d

= 7 + (23-1)(4)

= 7 + (22 × 4)

= 7 + 88

= 95

Hope you get your answer