Снаряд, летевший со скоростью 400 м/с, в верхней точке

The projectile flying at a speed of 400 m / s, at the upper point of the trajectory exploded into two fragments. The smaller fragment whose mass is 40% of the mass of the projectile flew in the opposite direction at a speed of 150 m / s. Determine the speed of larger fragments.

Task 10006. Detailed solution with a short recording conditions, laws and formulas used in the decision, the withdrawal of the calculation formula and the answer.