) Complete the following activity to find the sum of all natural numbers between
1 and 81 divisible by 6.
Answers
Answered by
3
Answer:
6,12,18---------------------------78
a = 6
d = 6
an = 78
an = a+(n-1) d
78 = 6+(n-1) 6
72 = (n-1)6
12 = n-1
n = 13
s13 = 13/2(12+(13-1)6)
13/2×(12+72)
13/2×84
13×84/2
13×42
546
Answered by
5
Answer:
546
Step-by-step explanation:
6,12,18,24,30,36,42,48,...78 is an AP(multiples of 6 btwn 1 and 81)
n=13 a=6 d=6
S13= 13/2[ 2×6 +(13-1) 6]
=13/2 [12+72]
=13/2×84
= 13×42
=546
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