Question

a=5,l=45,sn=400 find number of term and comman difference​

Answer 1

Answer:

n= 16 And d= 8/3

Step-by-step explanation:

Given that :

a=5

l=45

Sn=400

We know that, if last term is given , we can use this formula - Sn= n/2 (a+l)

Putting the value 400= n/2 (5+45)

400= n/2 (50)

400×2 = n (50)

800 /50 = n

n = 16

Now, we finding common difference d

We use normal formula Sn = n/2 [2a+(n-1) ×d]

Putting the value 400=16/2 [2×5 + (16-1)×d]

400=8 [10+15d]

400/8 = 10 +15d

50-10 = 15d

40/15 =d

d= 8/3

Hence , Number of terms. ( n) = 16

Common difference (d) = 8/3