1) Distance is same both ways, speeds are constant, therefore we can calculate the average speed using the formula -N:Dure wrote:??
2S1*S2/S1+S2
Lexy's average speed = 2*5*15/5+15 = 7.5
Ben's speed = 7.5/2
Time spent = Distance / speed = 5+5 / 7.5/2 = 10*2/7.5 = 20*2/15 hrs.
In minutes = (20*2/15)*60 = 160 minutes. Option D.
2) angle CAB = 45, angle COB = 2 * angle CAB = 2*45 = 90.
Area of sector covered by COB = 90/360(pie*r^2) = 1/4(pie)*2^2 = pie ......... (1)
Shaded region = area of sector covered by sector + area of triangle COA.
area of triangle can be calculated as = 1/2*(b*h) ; base and height are both 2.
THerefore are of triangle = (1/2)*2*2 = 2...........................................................(2)
Area of shaded region = (1)+(2) = pie + 2. Option B.
3) x^2-y^2 = 12; x^2-y^2 = (x-y)(x+y) = 12; x+y=3; using x+y; (3)(x-y)=12. Therefore x-y = 4.
Option D.
