Question

Find the sum of all natural numbers between 100 and 300 [(a) including both of these and (b) excluding both of these]:
(i) which are exactly divisble by 4, (ii) which are exactly divisible by 5,
(iii) which are exactly divisible by 4 and 5, (iv) which are exactly divisible by 4 or 5,​

Answer 1

(i)a=104 d=4 an=208

an=a+(n-1)d

208=104+(n-1)4

104÷4=n-1

26+1=n

n=27

sn=n/2(a+an)

27/2(104+208)

27/2×312

27×156

4212

Answer 2

Answer:

Step-by-step explanation:

Use the formula tn=a +(n-1)d and when u will find the value of n then use the formula of

Sn=n/2[2a+ (n-1)d]