Distance covered in first 5sec .​h1​=0+21​a(5)2 h1​=225a​​ distance covered in first 10sec S2​=0+21​a(10)2=2100a​ So distance covered in second 5sec. h2​=S2​−h1​=2100a​−225a​=275a​ distance covered in first 15sec. S3​=0+21​a(15)2=2225a​ so distance covered in last 5sec. h3​=S3​−S2​=2225a​−2100a​=2125a​ using (1), (2) and (3) equation.​225a​h1​​=275a​h2​​=125ah3​​h1​=3h2​​=5h3​​​