x varies directly as y but inversely as z.if y is increased by 30% and z is decreased by 30%,how does x vary?
问题描述：
x varies directly as y but inversely as z.if y is increased by 30% and z is decreased by 30%,how does x vary?
答
本人英语水平有限,恕无法用英语回答~!
这是一题数学上的比例问题.
X正比于Y,即设X＝KY,则当Y上升30﹪时,X也上升30﹪,即1.3X；
且X反比于Z,即X正比于1/Z,所以设X=K·1/Z,Z下降30%,则变为(10/7)·X.
所以,两个X是不同的!Understand?
就这样了!o(-"-)o