Help me with GMAT prep question

[nhai2003]

The cost of delivery for an order of desk chairs was $ 10.000 for the first chair, and $ 1.00 for each additional chair in the order. If an office manager placed an order for n desk chairs, is n >24?

1. The delivery cost for the order totaled more than $ 30
2. The average (arithmetic mean) delivery cost per chair of the n chairs was $ 1.36

Thanks guys!

[Vemuri]

IMO B.

Stmt1: Lets consider the minimum delivery cost to be $31. That means there were 1($10)+21($1) = 22 orders, which is less than 24. But, if you consider the delivery cost to be $50, then there are 41 orders, which is more than 24. So, not sufficient.

Stmt2: If the average of n chairs is $1.36, we can setup the equation:
($10+$1(n-1))/n = $1.36. On solving, you will get n=25. Sufficient.

Hope this helps.

[nhai2003]

Vemuri,

where you get the "n-1"'??
I dont understand it

[Vemuri]

Vemuri,

where you get the "n-1"'??
I dont understand it

Ok, we know the formula for Average = Total/# of items. From the question stem we know that the first item costs $10 & then $1 for the rest (n-1) items. So, the total is $10+$1(n-1).

I Hope it is clear now.

[nhai2003]

OA is B. Thanks Vemuri!