A ball, thrown vertically upward, rises to a height of 80 m and returns to its original position. The magnitude of its displacement after 7 s of motion will be ____. (take g = 10 m/s2)
The denominator of a rational number exceeds its numerator by 10. If the numerator is increased by 4 and the denominator is reduced by3, the number obtained is 5/6. The original rational number is