Question

3.Find the sum of all three digit
numbers which are divisible by 11​

Answer 1

Step-by-step explanation:

all three digit number that are divisible by 11 =110+121+131+141+151+161+171+181+191+210+220+230+240+250+260+270+280+319+310

Answer 2

The least 3 digit number that is divisible by 11 is a=110

The highest 3 digit number that is divisible by 11 is l=990

d=11

Last term is l=a+(n−1)d

990=110+(n−1)11

880=(n−1)11

n−1=

11

880

n−1=80⇒n=81

The Sum of the series is given as

S

n

=

2

n

[2a+(n−1)d]

S

81

=

2

81

[2(110)+(81−1)11]

=

2

81

[220+880]

=81×550=44550