Question

Tommy has taken a job in which he earns $1 on the first day of the month, $2 on the second day, $3 on the third, and so on. How much money will he earn in the month of October?

Answer 1

what is 1+2+3+...+31

total pay=average pay*number days=31/2 * 31

total pay=31^2/2

check my thinking

Answer 2

You can do it the hard way with
1+2+3+4+5+6+7+8+9+10+.........31 = ?

Answer 3

1+2+3
average is (1+3)/2 = 2
2*3 = 6 check :)

so I think it is
(1+31)/2 = 16
16*31 = 496