Answer:
if it is necessary to calculate astutely
63*5 = 70*5 - 7*5 = 315
78*9 = 78*10 -78 = 702
57*16 = 60*16 - 3*16 = 912
62*4 = 60*4 + 2*4=248
39*9 =40*9 - 9=351
1 )63*5=315
2)78*9=702
3)57*16=912
4)62*4=248
5)39*9=351
Explanation:
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