2.23×6.8所得的积是____位小数,结果是____.
计算:1﹣2+3﹣4+5﹣6+…+2007﹣2008+2009﹣2010+2011.
7560000000____ 980000000____
12540000000____ 1452000000____
对于化学反应X+Na2CO3=2Y+CaCO3↓的分析错误的是( )
— It's dangerous to swim here. Look at the sign.
— Oh, I notice it. Thanks for telling me.