在一次警察追捕小偷的过程中，小偷在警察前90m处，小偷逃跑的速度是5m/s，警察追捕的速度是27km/h，如果小偷和警察都做匀速直线运动，问：

计算：$\sqrt{\frac{1}{4}}-\sqrt[3]{8}+\sqrt{0.25}$

    Tai Lihua is a Chinese woman. She is very beautiful. As a child, she became deaf and dumb(哑的). She couldn't hear or say. She was very sad. Later, she had a teacher. The teacher taught her to dance. Though she couldn't hear, she was very hard­working. She danced very well. Now, she is very famous. She is not sad any more.