Answer:
C
Step-by-step explanation:
If order matters, then there are 12 ways to do this
If order does not matter, then there are 6 ways to do this
===========================================
We have 4 choices for the first slot and 3 choices for the next (we can't reuse a letter) so that's where 4*3 = 12 comes from
If order doesn't matter, then something like AB is the same as BA. So we are doubly counting each possible combo. To fix this, we divide by 2: 12/2 = 6
To be more formal, you can use nPr and nCr to get 12 and 6 respectively (use n = 4 and r = 2)
If 68 minutes ago it (then) was three times as many minutes past 10 am (now)
x + 68 = 3 ×
×
(120 - x) →
→
x = 73 min
… if 68 minutes ago it (now) was three times as many minutes past 10 am (then)
x = 3 ×
×
[120 - (x + 68)] →
→
x = 39 min
… if 68 minutes ago it (then) was three times as many minutes past 10 am (then)
x + 68 = 3 ×
×
[120 - (x + 68)] →
→
x = 22 min
I think x = 2 is the answer
