中一「數學」【有向數[ 1 ]】( 共 2 題 )

1. 4 +5+(-2) /
4+5-2
2. -15 + 35
if the answer is positive , then he is heavier
if the answer is negative , then he is lighter
if he is heavier ,
35-15 can find out he 重了多少

1.4+5-2

2.重了，35-15

1)4+5-2=7
2)y-15+35

1. ) 一架升降機從 4 字樓開始移動，它首先上升 5 層，再下降 2 層。問這架升降機最後的位置是在哪一層樓 ?

４＋５－２

2. ) 今年初小明的體重比去年減了 1 5 磅，但到年底卻增加了 3 5 磅，與去年比較他究竟輕了還是重了? 輕了或重了多少磅 ?

－１５＋３５

答案係負數就係輕左，答案係正數就係重左

Answer 1) 4th level is the "constant" here, escalate 5 level, 4+5=9, the plane went down 2 level later, 9-2=7, the plane is eventually flying at the 7th level.

Answer 2) We take "X" as xiaoming's weight for last year, x-15pounds is his weight this year, coming to the end of the year xiaoming gain another 35pounds, which is x-15+35=x+20, or (gain 35pounds)-(lost 15 pounds), compare to last year, he gains 20pounds.

e.g: If "X" is 40pounds, xiaoming will be 60pounds end of this year.

1)4+5-2
2)重了；重了=-15+35

1)4+5-2

2)Let y be 去年小明的體重,

y-15+35，重了