I think the answer is the last one.
a = 46c....for c
a/46 = c
322 = 46c
322/46 = c
7 = c.....7 circuits are required
Okay... so we have three places the automobiles can come in.
_ _ _
Now, how many automobiles have a chance of being in first place?
10.
Now, how many automobiles have a chance of being in second place now that the first place slot is taken?
9.
Now, how many automobiles have a chance of being in third place if the first and second place slots are taken by one automobile?
8.
Now multiply the numbers together to find the number of situations.
10 x 9 x 8 = 720.
