Matt gets a $1,300 commission on a big sale. This commission alone raises his average commission by $150. If Matt's new average commission is $400, how many sales has Matt made?  Choose the most appropriate option.
A) 3 B) 4 C) 5 D) 6 E) 7
Let, Average Commission = x   No. of items sold = y   Total Commission = xy   New Commission = xy+1300   New Average = (xy+1300) / (y+1) = 150+x   i.e. (xy+1300) = (y+1)* (150+x)   i.e. (xy+1300) = (xy+x+150y+150)   i.e. (1150) = (x+150y)   New Commission = 400 = 150+x   i.e. x=250   i.e. y = 6   New Sales = y+1 = 7   Answer: option 6
<result>D</result>
Matt gets a $1,300 commission on a big sale. This commission alone raises his average commission by $150. If Matt's new average commission is $400, how many sales has Matt made?