Consider the question. Arthur knows that he needs to finish 800 pages of reading over the summer. He has read 80% of a 500-page book and 1/5 of a 1000 page book. How many more pages does he need to reach to meet his goal?
 If the answer is '200'; explain the reasoning:
He read 400 pages from the 500 page book because 500 x .8 = 400. He read 200 pages from the 1000 page book because 1000 x (1 / 5) = 200. He has read 600 pages in total. He needs to read 200 more pages to reach 800 pages because 800 - 600 = 200.