Question

Heya !!

➡ Find the sum of Numbers Which are divisible by 7 between 100 and 1000.

➡ Give Correct answer.

✌✌

Answer 1

heya dear

here is your answer

The numbers which are divisible by 7 between 100 and 1000 are 105,112,119.........994

here

, a= 105

d = 7

tn = 994

so, tn = a+(n-1)d

994 = 105+(n-1)7

994 = 105+ 7n - 7

994 = 98 + 7n

n = 896/7

n = 128

sum = n/2 ( 2a +(n-1)d )

= n/2 ( a+tn)

= 128/2 (105 + 994)

= 70336

i hope it helps uh

thanks !!!

Answer 2

hey dear



< riya 113 sister >



solution

The first number after 100 divisible by 7 is

105 and last before 1000 is 994



Thus


a = 105

l = 994

d = 7


n = ?



From 994 , n can be obtained


an = a + ( n - 1 ) * d


994 = 105 + ( n-1) 7



994 - 105 = ( n -1) 7


889 /7 = (n -1)


127 = ( n - 1)

n. = 127 +1

n = 128




Now sum of 128 terms = n / 2 ( a + l)

= 128 /2 ( 105 +994)

= 64 * 1099

= 70, 336



< hence sum is 70,336 >



hope it helps


thank you