if the average of 7 sales is 400$, than in total he had to earn 2800$ in 7 sales

he made: 1000+700+250+200+100 = 2250$ in 5 sales

so in the the last 2 sales he had to make a comission of 550$
meaning he had to sell in an amount of 5500$

Hey!!! this is the way u do it :

he wants to dowble his commission from $400 to $800

100+200+250+700+1000+x+y
---------------------------------------- = 800
7

i.e 2250+x+y = 5600
x+y = 3350

Now he has to sell
10/100 * z = 3350
z= 33500

He has to sell 33500 in order to double his average

Yes

i didnt notice they said 'doubled'

but anyway, the method is the same ...

The asnwer is correct if we assume that he sells during seven days. However, it could also be the case that there are only 5 days. Note that problem stated that he made five sales during the the week and 2 sales on the last day of the week.

here's the OA:

The two sales on Matt's last day of the week must total $33,500.

(100 + 200 + 250 + 700 + 1000 + x) / 7 = 800
x = 3350
since x is Matt's 10% commission, the sale is $33,500.

Assuming the two sales on Matt's last day of the week must total $33,500.

(100 + 200 + 250 + 700 + 1000 + x) / 7 = 800
2250+ x = 5600
x= 5600-2250
x = 3350
since x which is the 10% Matt's commission, then the sale is $33,500.