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Amrabdelnaby
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Let's assume Joanna bought X number of $0.15 stamps and Y number of $0.29 stamps.
Statement 1 : she bought 4.4$ worth of stamps
This implies:
(0.15)X + (0.29)Y = 4.4
15X + 29Y = 440 (multiply both sides by 100)
15X = 440 - 29Y
X = (440 - 29Y) / 15
This tells that the subtraction (440 - 29Y) will be a multiple of 15, because we can't have fractional amount of stamps.
Now list out various multiples of 15
0,15,30,45,60,75,90....
Notice that every time the number ends in either a 5 or a 0. This should mean that 440 - 29Y must also end in either a 5 or a 0
The unit digit of 440 is 0 , so the only way to subtract something from it (to get a number which ends with a 5 or 0) is to subtract a number whose unit digit ends in a 5 or 0
Now its fairly simple. 29 * 5 = 145 or 29 * 10 = 290 (9 multiplied by a 5 or a multiple of 5 or a 0 will satisfy this ,notice that only those two will give us the desired result)
440 - 145 = 295 --> Not divisible by 15
440 - 290 = 150 --> Divisible by 15
So, X = 10 and from our previous equation Y = 10
SUFFICIENT
Statement 2 : she bought an equal number of 0.15$ stamps and 0.29$ stamps
Joanna could have bought any number of both $0.15 and $0.29 stamps
NOT SUFFICIENT
Correct Answer : A
