Joanna bought only $0.15 stamps and $0.29 stamps. How many $0.15 stamps id she buy?
1. She bought $4.40 worth if stamps
2. She bought an equal number of $0.15 stamps and $0.29 stamps.
Let F and T be the number of $0.15 stamps and $0.29 stamps purchased
1. She bought $4.40 worth if stamps
0.15*F + 0.29*T = 4.40
15*F+29*T = 440
440 is a multiple of 10 so the unit's digit of 29T should be 5(If the unit's digit of 15*F is 5) or 0(If the unit's digit of 15*F is 0)
If T = 5, 15F = 440 - 29T = 440 - 145 = 295; 15F = 295; F is not an integer, so T != 5
If T = 10, 15F = 440 - 29T = 440 - 290 = 150; 15F = 150; F = 10 So the value of T may be 10
If T = 15, 15F = 440 - 29T = 440 - 435 = 5; 15F = 5; F is not an integer, so T! = 15
For any value of T > 15 (Where T is a multiple of 5) the value of F is < 0, which is not possible.
So, the value of F = 10. Sufficient!
2. She bought an equal number of $0.15 stamps and $0.29 stamps.
Insufficient!
Answer :
A
I am wondering if anyone has any tips they use when looking at Data sufficiency questions ? This is my weaker area so any help would be super beneficial
As Shankar already mentioned it is all about practise and execution. Some piece of advice below.
a) Study the question and conditions carefully such as
e.g.If x>1 , Is (x+1)/2 is an integer ?,
If x>1 is the condition here
b) Simplify/Rephrase the question (especially word problems)
e.g. If x>1, What is the value of (x^2+3x+2)/(x+1) ?, Can be rephrased to
If x>1, what is the value of (x+2)?
c) Don't calculate except when necessary.
e.g. If x>1, Is (x^2+3x+2)>0 ?, Can be rephrased to Is (x+2)(x+1)>0?
1) x = -1.5
2) x = -3/2
In the above case, you need not substitute the value of x=-1.5 in the equation (x+2)(x+1). If x = -1.5, you know that the value of x+2 > 0 and the value of x+1 < 0. So,
(x+2)(x+1)<0 in both the cases.
d) Look at each of the two statements independently of the other.
Please find below a few urls which will of help!
https://www.beatthegmat.com/mba/category ... ufficiency
https://www.beatthegmat.com/tips-for-dat ... 95843.html
https://www.beatthegmat.com/dana-s-quant ... 37055.html
Practise, Practise and more Practise is the mantra here !
