В начальный момент времени было 1000 атомных ядер изотопа с периодом полураспада Т1/2 = 5 мин. Сколько не распавшихся ядер

We will have clean air if we protect the nature on our fragile planet.
Our family will have a picnic if it isn't foggy and rainy weather the day after tomorrow.
My friends will give the bread to the pigeons when they visit the Trafalgar Square.
If I have a lot of money, I shall give it to the ill children