Describe a way to make the problem easy to solve mentally 4

Describe a way to make the problem easy to solve mentally:

4 x 99, 12 x 25 and 16 x25

Solution

For 4*99: As 99 is very closer to 100, multiply 4 with 100 and subtract by 4 to get the answer.

4*99=4*100-4= 396

For 12*25: Remember for every 4 multiple, 25 accounts to 100. In 12 we have 3 four multiples. Therefore answer would be 300.

For 16*25: In 16 we have 4 four multplies, therefore from previous question this accounts to 400. 4*4*25=4*100=400