1.

Number of ways in which three distinct numbers can be selected between 1 and 20 both inclusive, whose sum is even is______.

Answer»


Solution :All even +2 ODD 1 even
`""^(10)C_(3)+""^(10)C_(2)XX""^(10)C_(1)`
`(10xx9xx8)/(6)+(10xx9)/(2)xx10`
`120+450+570`


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