Question

find the sum of all natural numbersb less than 200 divisible by 7​

Answer 1

Answer:

2842

Step-by-step explanation:

Let's form an A.P to solve the problem

A.P = 7 ,14 ,21 , ....,196

a1 = 7

a2 = 14

d = a2 - a1

= 14 - 7

= 7

an = 196

W.k.t an = a +(n-1)d

an = a+(n-1)d

196 = 7 + (n-1) 7

196-7 = (n-1)7

n-1 = 189 / 7

n-1 = 27

n = 27+1

n = 28

Now , Sn = n/2 {a + an}

Note : This formula is used when an is given.

or Sn = n/2 {2a + (n-1)d}

So,

S28 = 28/2 {7+196}

= 14 × 203

= 2842

Therefore, the sum of all the numbers divisible by 7 less than 200 is 2842.