单发天弓三拦截机率百分之70
三发天弓三拦截机率为
一发拦截成功 两发失败机率
3×0.7×0.3×0.3
两发拦截成功 一发失败机率
3×0.7×0.7×0.3
三发拦截成功机率
0.7×0.7×0.7
3×0.7×0.3×0.3+3×0.7×0.7×0.3+0.7×0.7×0.7
=0.973