2. Xinxin Shopping Mall: (500+125) × 3+125 = 2000ml, so the cost is: 8×3+ 1×2.2=26.2 yuan.

Guangxin market: 500× 4 = 2000ml, then: 8×4=32 yuan > 30 yuan, after 20% discount = 32× 80% = 25.6 yuan < 26.2 yuan.

So, my mother went to Guangxin market to buy cheap ones.

3.5000× 2.25 %× 3 = 337.5 yuan

5000× 3.24% = 162 yuan

5000× 3.60% = 180 yuan

So, dad may choose to save it once a year. (But in real life, the bank's interest rate is not calculated like this, but it is a five-year transaction. )

4. (320× 38.5%) ÷1.5 = 80km (8: 00 to 9: 30 =1.5h)

320÷80=4 hours

4+8 =12 >11:30, so I can't go to Ningbo.

5. If A: 50=4× 10+4×2+2, it needs: (40+2)×25= 1050 yuan.

B cost: 50× [25× (1-20%)] =1000 yuan.

C: 50×25= 1250 yuan =( 1200+50) yuan, then you can return 1200÷ 100×20=240 yuan.

Actual cost1250-240 =1010 yuan.

1000 yuan <10/0 yuan < 1050 yuan, so Yanjiang Village Primary School should go to Store B to buy football.