wat is the sum of all integers divisible by 8 that are between 100 and 200?
how will i solve for it?
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Here’s how you do it:
First find how many such integers are there between 100 and 200 that are divisible by 8. Obviously, these must form an Arithmetic Progression with a common differece = 8 (Agreed?)
First number after 100 divisible by 8 is 104. 200 itself is divisible by 8
200 = 104 +8*(n-1) (For nth term of an AP)
n = 13
Sum to n terms of an AP = 13/2(104+200) = 13*304/2
= 1976
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104 = 8 X 13
112 =8 X 14
120 =8 X 15
etc.
So, answer is:
104 + 112 + 120 + 128 + 136 + 144 + 152 + 160 + 168
+ 176 + 184 + 192 + 200 = 1976
Easy.
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