A grocery store sells apples by the pound. If the price per

=>

Suppose p is the current price of apples at the grocery store. Then
12/p – 12/(p+1) = 0.4
=> 12(p+1) – 12p = 0.4p(p+1) if we multiply both sides by p(p+1)
=> 12 = 0.4(p2+p)
=> 30 = p^2+p after multiplying by 2.5
=> p^2+p-30 = 0
=> (p-5)(p+6) = 0
=> p = 5, since prices cannot be negative.

Therefore, the answer is C.

Answer: C

Max@Math Revolution wrote:[GMAT math practice question]

A grocery store sells apples by the pound. If the price per pound is increased by $1, $12 will buy 0.4 pounds less of apples than if the price remains at the current level. What is the current price per pound of apples at the grocery store?

A. $4
B. $4.5
C. $5
D. $5.5
E. $6

We can PLUG IN THE ANSWERS, which represent the current price per pound.
When the correct answer is plugged in, a $1 increase in the price will decrease the amount that can purchased by 2/5 of a pound.
Notice the following:
The amount that can purchased with $12 = 12/(price per pound).
The fraction in blue has a DENOMINATOR OF 5.
Thus, the correct answer is probably C (which indicates a current price of $5 per pound) or A (which will yield a price of $5 per pound after the $1 increase).

C: $5 per pound
At a current price of $5 per pound, the amount that be purchased with $12 = 12/5 pounds.
If the price increases by $1 to $6 per pound, the amount that can purchased with $12 = 12/6 = 2 pounds.
Difference between the two amounts = 12/5 - 2 = 12/5 - 10/5 = 2/5.
Success!

The correct answer is C.