Question

In an AP, if a = - 5, last term = 21 and Sum= 200, then n is equal to

Answer 1

Answer:

we know that, s= (a+l)n/2

where l= last term

• 200= n/2(-5+21)
• 400= n(16)
• n= 400/16

Answer 2

◆ a = -5

◆ last term = 21

◆ sum = 200

◆ n = ?

Formula :-

→ Sn = n/2( a+ l)

→ 200 = n/2 ( -5 + 21 )

→ 200 * 2 = n ( 16 )

→ 400 = 16n

→ n = 400/16

→ n = 25

Hence,

• n = 25 $\sf$