In developing the ways of calculating time, astronomers divided an hour into 60 minutes. why is 60 a better choice than 59 or 61?

60 was chosen because it's the smallest round number divisible by the first six counting numbers. Not only that, but it is also divisible by 10, 12, 15, 20 and 30, all being numbers important for calculating time.

On monday,mrs.wise bought 3 lbs of apples at $4per lb= 4*3=$12on tuesday ,20%off and she buy 5 lbs of apples = $4-20%=3.20*5lb=$16example: other wise when she buy 5lbs on monday she have to spend 4*5=20