Alfred is practicing typing. The first time he tested himself, he could type 45 words per minute. After practicing for a week, he could type 48 words per minute. After two weeks he could type 51 words per minute. Based on this pattern, predict how fast Alfred will be able to type after 4 weeks of practice.

The first thing to do would be to minutely read the question. This will solve half the problem. Most of the information's required are already given in the question. Let us write them down first.

Starting - 45 words per minute

After 1 week - 48 words per minute

After two weeks - 51 words per minute

From the above information's, we can conclude that Alfred increases his speed of writing by 3 words per week. Then

After 3 weeks - 54 words per minute

After 4 weeks - 57 words per minute.

From the above deduction, we can conclude that after 4 weeks, Alfred can type 57 words per minute.