Question

5. Find the number of terms in each of the following A.P.

1. 7, 13, 19, …, 205

2. 18,15 1/2 ,13, ..., -47
​

Answer 1

Answer:

Mark as a brilliant please

Answer 2

Answer:

Hope it help

Step-by-step explanation:

1 First term, a = 7

Common difference, d = a2 − a1 = 13 − 7 = 6

Let there are n terms in this A.P.

an = 205

As we know, for an A.P.,

an = a + (n − 1) d

Therefore, 205 = 7 + (n − 1) 6

198 = (n − 1) 6

33 = (n − 1)

n = 34

2 First term, a = 18

Common difference, d = a2-a1 =

Ncert solutions class 10 chapter 5-4

d = (31-36)/2 = -5/2

Let there are n terms in this A.P.

an = -47

As we know, for an A.P.,

an = a+(n−1)d

-47 = 18+(n-1)(-5/2)

-47-18 = (n-1)(-5/2)

-65 = (n-1)(-5/2)

(n-1) = -130/-5

(n-1) = 26

n = 27