Data Sufficiency

Yesterday, D spent total of 240 minutes attending a class, responding to Emails, and talking on the phone. If she did no two of these three activities at the same time, how much time did she spend talking on the phone?

(1) Yesterday, the amount of time that D spent attending the class was 90% of the amount of time that she spent responding to Emails.

(2) Yesterday the amount of time that D spent attending the training class was 60 % of the total amount of time that she spent on Emils & talking on the phones.

C

Since she spent no time doing two activities at once, the question stem lets us set up the equation

c+e+p = 240

where c = minutes in class, e = minutes using email, and p = minutes on phone.

Statement (1) gives us another equation... c = 0.90e. We can plug this into the original equation to get

0.90e + e + p = 240 = 1.9e + p

however, we still have two unknown values in this equation and cannot solve for p.

Statement (2) gives us the equation c = 0.6(e+p). Again, we could plug this into the original equation to get

0.6e+0.6p+e+p = 240 = 1.6e+1.6p

but we still have 2 unknown values and cannot solve for p.

(1) and (2) Combined give us two different equations for c. We can then set them equal to each other...

c = 0.90e = 0.6(e+p)
0.30e = 0.6p
0.50e = p

Now, we have p in terms of e. Statement(1) gave us c in terms of e. Combining these we can arrive at

c+e+p = 240
0.90e+e+0.50e = 240
2.4e=240
e=100

0.50(100) = p
p=50

c=0.90(100)
c=90