Question

Find the sum of all 3-digit natural numbers,which are multiples of 11

Answer 1

118,762 is the sum of all 3-digit natural numbers,which are multiples of 11 ...

Please mark it as brainiest answer ...

Answer 2

Answer:

list of all 3 digit numbers divisible by 11 are:

110,121, 132, ..............................,990

in the given AP ;

a = 110

d = 11

l = an = 990

an = a+(n-1)d

990= 110 + (n-1) 11

990 - 110 = (n-1) 11

880 = (n-1) 11

880/11 = n-1

80 = n-1

80 + 1 = n

81 = n

To find the sum of these digits ;

sn = n/2 [ a + l ]

s81 = 81/2 [ 110 + 990 ]

s81 = 81/2 [ 1100 ]

s81 = 81 / 2 * 1100

on solving it ; we get ,

s81 = 81 * 550

s81 = 44,550

therefore , required sum is found.

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