We expect 150 defects out of the 10,000 cars if the 3 defects out of the 200 cars sampled is representative of all 10,000 cars.
First, let's set up the proportions. We have 3/200 cars with defects and we want to know X for X/10000. So
3/200 = X/10000
Now solve for X.
3/200 = X/10000
10000*3/200 = 10000 * X/10000
30000/200 = X
150 = X
So the answer is:
We expect 150 defects out of the 10,000 cars if the 3 defects out of the 200 cars sampled is representative of all 10,000 cars.