从2开始,连续的偶数相加,它们和的情况如表: 加数的个数n 连续偶数的和S 1 2=1×2 2 2+4=6=2×3 3 2+4+6=12=3×4 4 2+4+6+8=20=4×5 5 2+4+6+8+10=30=5×6
计算270×30时,先算___,最后在积的末尾添上___个0,积是___位数,相当于27×3的积乘___.
3. Go to work on foot instead of by bus every day. 4. Take a walk after supper every day. Food 1. Have only a glass of milk and an egg for breakfast every morning. 2. Just have fruit for supper three times a week. 3. Eat more vegetables and less meat for dinner. 4. ...
Mrs. Ball has a son. His name is Mick. She _ _1_ _ him very much and as he is not a __ 2 __ child, she is always _ _3_ _ that he may be ill, _ _4_ _ she takes him to see the best _ _5_ _ in the town four times a year and the doctor always looks