Data Sufficiency

Joanna bought only $0.15 stamps and $0.29 stamps. How many $0.15 stamps did she buy?


(1) She bought $4.40 worth of stamps.
(2) She bought an equal number of $0.15 stamps and $0.29 stamps.


OA: A

Let number of $0.15 stamps = x
number of $0.29 stamps = y

statement 1
x(0.15) + y(0.29) = 4.40

two unknowns 1 eq - Not Suff.

statement 2
x = y------------------Insufficient

Together

Sufficient. imo C

I don't know how it is A

From 1, We have .15x+.29y=4.40
We may think that since we have 2 variables, we cant solve this equation, but if we plug values we will get the answer.
Since this equation contains a value of 0.29, and the total is 4.40, the stamps with value of 0.29 is a multiple of 5.
only x=10,y=10 fits the bill.
Hence suff.

From 2, we have x=y but still we dont know the total. hence insuff.

Hence A.

jimmiejaz wrote:From 1, We have .15x+.29y=4.40
We may think that since we have 2 variables, we cant solve this equation, but if we plug values we will get the answer.
Since this equation contains a value of 0.29, and the total is 4.40, the stamps with value of 0.29 is a multiple of 5.
only x=10,y=10 fits the bill.
Hence suff.

From 2, we have x=y but still we dont know the total. hence insuff.

Hence A.

Nice explanation..