Question

1+3+5+...+x=1600

Answer 1

1 + 3 + 5 + ... + x = 1600

{ n - 1 ) / ( 2 ) + 1 } ^ 2 = 1600

( n - 1 ) / ( 2 ) + 1 ) = 40 ^ 2

( n - 1 ) / ( 2 ) + 1 = 40

( n - 1 ) / ( 2 ) = 40 - 1

( n - 1 )  / ( 2 ) = 39

n - 1 = 39 x 2 

n - 1 = 78 

n = 78 + 1 

n = 79

Answer 2

1 + 3 + 5 + ... + x = 1600

{ n - 1 ) / ( 2 ) + 1 } ^ 2 = 1600

( n - 1 ) / ( 2 ) + 1 ) = 40 ^ 2

( n - 1 ) / ( 2 ) + 1 = 40

( n - 1 ) / ( 2 ) = 40 - 1

( n - 1 )  / ( 2 ) = 39

n - 1 = 39 x 2 

n - 1 = 78 

n = 78 + 1 

n = 79

Answer 3

1 + 3 + 5 + ... + x = 1600

{ n - 1 ) / ( 2 ) + 1 } ^ 2 = 1600

( n - 1 ) / ( 2 ) + 1 ) = 40 ^ 2

( n - 1 ) / ( 2 ) + 1 = 40

( n - 1 ) / ( 2 ) = 40 - 1

( n - 1 )  / ( 2 ) = 39

n - 1 = 39 x 2 

n - 1 = 78 

n = 78 + 1 

n = 79