What should come at place of question mark (?) in the following number series?

15 20 50 165 680 ? 

Direction : What value should come in the place of question mark (?) in the following questions?

$$({144\over16}×{828\over 9})=?+325 $$

In 16 minutes, the minute had gains over the hour hand by

If the difference of the compound interest and the simple interest on a sum of money for 3 years is Rs. 186. Find the sum of money, if the rate of interest in both cases be 10 % 

Two numbers are in the ratio 3: 4 if their LCM  is 240 then smaller number will be

Water flows in to a tank 15 m.×10 m. through a rectangular pipe 2 m.×1.5 m. at 20 km./hr. In how much time will the water level in the tank rise by 3m.?

If a line has one end (4,0) and the middle point (4,1), what will be the directions at the other end of the line?

What is the L.C.M of 12, 23, 24?