Leo has to write a 400-word story for his literature class. 10 words fit on each line of his notebook and 20 lines fit on each page. Lucas has filled one and a half pages. How many words does he have left to write? Think carefully first, then make a decision:
Half a page is 20 / 2 = 10 lines. In total, he has written 20 + 10 = 30 lines. The 30 lines written are 30 * 10 = 300 words. Lucas has 400 - 300 = 100 words left to write. So, the answer is 100.