Silvia wants to mix a 20% apple juice drink with pure apple juice to make 4 L of a juice drink that is 80% apple juice. How much pure apple juice should she use?​

Which of the following are parts of a sphere

Which one ? is the answer and how to find this answer

How do i start to solve? would appreciate a walk-thru! a bird sitting 16ft above the ground in an apple tree dislodges an apple. after how many seconds does the apple land on the ground? (assuming that no branches will interfere with it's fall)