Question

find the sum of natural numbers between 91 no 171, which are divisible by 5​

Answer 1

Answer:

first of all write an a.p.:-

95,100,105.................170

then find no. of digits :-

an=a +(n-1)d

170 = 95 + (n - 1) 5

n = 16

then find sum of all digits

Sn= n^2/2 (2a +An)

= 256/2 (2*95 + 170)

Sn = 46080

answer is correct or not plzz tell me

Answer 2

The required sum of natural numbers is 2120

Step-by-step explanation:

To find the sum of natural numbers between 91 and 171 which are divisible by 5

Numbers are

95, 100, 105,................................. , 170

Now is forms an A.P.

Therefore

First we have to find the number of terms

as we know

let a is first term , d is common difference , n id number of terms ,$a_n$ is nth term and $S_n$ is sum of n terms $a_n$ = 170

we have a= 95 , d= 5,

$a_n=a+(n-1)d\\\\\Rightarrow 170 = 95+(n-1)5\\\\\Rightarrow 170-95=(n-1) 5\\\\\Rightarrow 75= (n-1)5\\\\\Rightarrow \dfrac{75}{5} =n-1 \\\\\Rightarrow 15 = n-1\\\\\Rightarrow n= 16$

There are 16 terms

Now

$S_n=\dfrac{n}{2} (a+a_n)$

$S_n= \dfrac{16}{2} (95+ 170)$

$S_n= 8\times 265 = 2120$

Hence the sum of natural numbers between 91 to 171 divisible by 5 is 2120

#Learn more

Find the sum of first 10 multiples of 3​

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