When multiplying by 4 you can use the strategy of double-double. For example, if the problem was 4 x 15, you double 15 (30) and then double 30, which equals 60.

Try solving some of these by using the double-double strategy and post your working out and answers in a comment under this post.

1) 4 x 18
2) 4 x 34
3) 4 x 62
4) 4 x 223