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Find the sum of all numbers from 150 to 200 which are divisible by 7.

Answer» Correct Answer - The sum is 1225
The numbers from 150 to 200 divisible by 7 are 154,161 ,168,…., 196
Here, `a= 154, d= 7 ` and `t_(n) = 196`
`t_(n) = a+ ( n -1)d` …(Formula )
`:. 196 = 154 + ( n-1) xx 7 ` …(Substituting the values )
`:. 196 - 154 = ( n-1) xx 7`
` :. ( 42)/(7) = n-1` `:. n -1 = 6` `:. n = 7`
Now, we find the sum of 7 numbers.
`S_(n) = (n)/(2) [t_(1) + t_(n)]` ...(Formula )
`= ( 7)/(2) [ 154 + 196)`
`= ( 7)/(2) xx 350`
` = 7 xx 175 `
`= 1225`


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