1, assuming that there is x in grade five and 200-X in grade four, if the equation 2x/7=2(200-x)/ 13 is listed, the solution x=70, and there is 130 in grade four, then1is needed in four and five years respectively.

2. The semicircle is translated to produce a rectangle. The area of crescent = semicircle-white arc, and white arc = semicircle-rectangle. So crescent area = rectangular area =8*2= 16.