2.3+23.4+34.5+45.6+56.7+67.8+78.9巧算
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/26 02:20:37
![2.3+23.4+34.5+45.6+56.7+67.8+78.9巧算](/uploads/image/z/4859-35-9.jpg?t=2.3%2B23.4%2B34.5%2B45.6%2B56.7%2B67.8%2B78.9%E5%B7%A7%E7%AE%97)
2.3+23.4+34.5+45.6+56.7+67.8+78.9巧算
2.3+23.4+34.5+45.6+56.7+67.8+78.9巧算
2.3+23.4+34.5+45.6+56.7+67.8+78.9巧算
2.3+23.4+34.5+45.6+56.7+67.8+78.9
=(0.3+0.4+……+0.9)+(2+3+4+……8)+(20+30+40+……70)
=(0.3+0.9)*7/2+(2+8)*7/2+(20+70)*6/2
=4.2+35+270
=309.2