②3.75÷0.45, ÷0.8, ÷ 1.5, < 10× 0.45, so the electricity consumption of household C is less than 10 and that of household B is greater than 10 and less than 20;

③7. 10÷0.8 cannot be divided, so the household electricity consumption is more than 20;

3.75÷0.45=8......0. 15

3.75=0.45×3+2.4=0.45×3+0.8×3

Therefore, the household electricity consumption of C is 10-3=7 kWh, and that of B is 10+3= 13 kWh;

7. 10÷0.8=8......0.7

7. 10=0.8×7+ 1.5

The electricity consumption of household A is 20+ 1=2 1 kWh;

Therefore, the electricity consumption of households A, B and C is 2 1, 13 and 7 kWh respectively.