Note that some of these three problems have a large amount of data, so it is necessary to convert large data into small data appropriately to reduce the amount of calculation.

1. Suppose you deposit 10000 yuan and 200000- 10000 yuan in Bank A and Bank B respectively.

A bank deposit x A interest rate+B bank deposit x B interest rate =0.46 million yuan.

1.5%x+3.5%(20-x)=0.46

The solution is x= 12.

Therefore, the deposits in Bank A and Bank B are 6.5438+0.2 million yuan and 80,000 yuan respectively.

2. X billion Treasury bills should be purchased.

The principal of purchasing national debt+interest after three years = 34,500 yuan.

x+5%x×3=3.45

x=3

So you need to buy 30 thousand yuan of national debt

The distance between terminal a and terminal b is x kilometers.

Ship speed = distance ÷ downstream time-current speed = distance ÷ upstream time+current speed

(x/8) -3=(x/ 12) +3

x= 144

So the distance is 144km.