Question

find the sum of all 2-digit natural numbers divisible by 5.
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Answer 1

Step-by-step explanation:

10+(n-1)*5=95,then n=18. Required sum=n/2(a+l)=18/2(10+95)=945.

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The sum of all two digit numbers divisible by 5 is.

Answer 2

Answer:

2430

Step-by-step explanation:

First term, a = 10

Common difference= 12-10

= 2

last term= 98

a+(n-1)d = 98

=> 2n = 98-10+2

=> n = 90/2

=> n = 45

Sum = n/2 [ 2a+(n-1)d]

= 45/2 [20 + 44×2]

= 45/2 [20 + 88]

= 45/2 × 108

= 45×54

= 2430