The double number line below shows the approximate number of kilograms in a certain number of pounds: Two number lines are shown one above the other. The number line on the top shows three long vertical lines. Between each longer vertical line, there is a shorter vertical line. There is one shorter vertical line after the last longer vertical line, thereby making a total of three shorter vertical lines. The longer vertical lines are labeled 3, 5, 7. On the right of this number, the line is written Pounds. The number line below it also has three long vertical lines and three shorter vertical lines. The first longer vertical line is ahead of the first longer vertical line of the top number line so that the first shorter vertical line on the lower number line is aligned with the first longer vertical line, labeled 3 on the top number line. The second longer vertical line is ahead of the second longer vertical line of the top number line so that the second shorter vertical line on the lower number line is aligned with the second longer vertical line, labeled 5, on the top number line. The third longer vertical line is ahead of the third longer vertical line of the top number line so that the third shorter vertical line on the lower number line is aligned with the third longer vertical line, labeled 7, on the top number line. The longer vertical lines on the bottom number line are labeled 1, 2, 3, respectively. On the right of this number, the line is written Kilograms. Based on the number line, about how many kilograms are there in 9 pounds? 3.50 4.00 4.50 5.00