Question

find the 20th term of the AP whose 7 term is 24 less than 11 term first term being 12​

Answer 1

Answer:

126

Step-by-step explanation:

In AP, nth term is a + (n - 1)d, a is first term abd d is common difference.

Let the common difference be 'd'.

Here,

= > 7 term is 24 less than 11 term

= > 7th term = 11th term - 24

= > 12 + (7 - 1)d = 12 + (11 - 1)d - 24

= > 6d = 10d - 24

= > 24 = 10d - 6d = 4d

= > 24/4 = d

= > 6 = d

So,

20 th term is:

= > 12 + (20 - 1)d

= > 12 + 19(6)

= > 126

Answer 2

Given:-

a = 12

a₇ = a₁₁ - 24

To find:-

20th term of the AP

Solution:-

a + 6d = a + 10d - 24

a-a + 6d-10d = -24

-4d = -24

d = -24/-4

d = 6

a₂₀ = a + 19d

a₂₀ = 12 + 19×6

a₂₀ = 12+ 114

a₂₀ = 126

Twentieth term (a₂₀) = 126