3 are not the car . They are the directions that they could get on a highway.

read carefully the stem.

Regards

I'm thinking of it this way: I have two cars because they will go to 1 direction I will consider them 1. Then they have 3 options they will take 1. 3C1. Why the answer as above ?

First::There are no mention of cars - it can be infinite number of cars.

But, we were given 3 direction, where the car can move.

Next, we need to find in how many ways cars can travel in exactly 2 direction i.e Left & Right , Left & Straight , Right & Straight

After u ve analysed the ques, now it's time to combine the possible ways.

STEP 1:

We ve 3 direction (LEFT, RIGHT & STRAIGHT) but we need exactly 2 : So this can be found by 3C2 ways

STEP 2:

Now we got 3 options to choose from Left & Right , Left & Straight , Right & Straight ; This can be found by 3C1 ( because we can only choose one option out of 3)

Step 3::

Next we only have got one option left to choose from 2 i,e ( if we have selected LEFT & RIGHT - one direction is already chosen and we are left with only one option) This can be found : 2C1 ways

Now combine them, you will get the answer.

Here's how I did it...

We have 3 spots. We can choose 2 of them to be the same. 3C2. Then that group can choose from 3 options for what they'll do. 3C1. The remaining spot can't repeat so it can only choose 1 of 2 options. 2C1.

Thus we have 3C2*3C1*2C1 which evaluates to 18.

tricky

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