Question

find all the sum of multiples of 7 lying between 100 and 1000.

Answer 1

Heya User,

--> 0_0 observe that 105 is the first multiple of 7 after 100 and 994 is the last one =_=

--> Now, we have to find the sum :->
   --> S = [ 105 + 112 + 119 + 126 + ... + 987 + 994 ]

=_= The creepiest part --> Applying A.P. formula :->

But for that --> 994 is which multiple of '7' -->
--> 994/7 = 142 || 105/7 = 15 || => 994 is -> { 142 - 14 } = 128th term after 105 

Now,
$S_{128} = \frac{128}{2} [ 105 + 994 ]$

which after calculation yields .. ummm, 
--> S₁₂₈ = 70336 ... Done ..

Answer 2

Answer:

Step-by-step explanation:

Heya User,

--> 0_0 observe that 105 is the first multiple of 7 after 100 and 994 is the last one =_=

--> Now, we have to find the sum :->

   --> S = [ 105 + 112 + 119 + 126 + ... + 987 + 994 ]

=_= The creepiest part --> Applying A.P. formula :->

But for that --> 994 is which multiple of '7' -->

--> 994/7 = 142 || 105/7 = 15 || => 994 is -> { 142 - 14 } = 128th term after 105 

Now,

which after calculation yields .. ummm, 

--> S₁₂₈ = 70336 ... Done ..

Read more on Brainly.in - https://brainly.in/question/2351755#readmore