Question

If an AP ia=-2.5, d = 0.5 an=7.5 then n is


قل​

Answer 1

Answer:

n = 19

Step-by-step explanation:

a = - 2.5

d = 0.5

an = 7.5

=> a + (n - 1)d = 7.5

=> (-2.5) + (n - 1)(0.5) = 7.5

=> - 2.5 + 0.5n - 0.5 = 7.5

=> - 2 + 0.5n = 7.5

=> 0.5n = 7.5 + 2

=> n = (9.5/0.5)

= 19

Answer 2

Answer:

Here, a= -2.5

d=0.5

an=7.5

Also,

we know that, an = a+(n-1)d

therefore, 7.5 = a+(n-1)d (b'coz an=7.5,given)

7.5 = -2.5+(n-1)0.5

7.5+2.5 = (n-1)0.5

10/0.5 = n-1

20 = n-1

20+1 = n

or n = 21

Hence, the required value of n is 21.