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Find the sum of all positive integers less than $1000$ ending in $1$ or $2$ or $3$ or $4.$

 Jan 13, 2024
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Note

 

sum 1 - 4 =  10

sum  11 - 14  = 50

sum 21 - 24  = 90

sum 31 - 34 = 130

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991 - 994  =  9910

 

Number of terms =  40 in each hundred  =   40 * 10  = 400

 

sum =  [10 + 9910 ]  [ 400 ]  / 2  =    198,400

 

 

cool cool cool

 Jan 13, 2024

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