[計量] 幾題想請問一下
1.
A store currently charges the same price for each towel that it sells. If the
current price of each towel were to be increased by $1, 10 fewer of the
towels could be bought for $120, excluding sales tax. What is the current
price of each towel?
Ans. $3
我從網路上找的解答:
current price-x
current quantity-y
x*y=120
current price increased by 1 =(x+1)
current quantity decreased by 10=(y-10)
(x+1)*(y-10)=120
solving two equations
x^2+x-12=0
x=3
但我困惑的是，我從文意中讀不出x*y=120這一項，然後來跟(x+1)(y-10)=120來解聯立
由原題我只能了解(x+1)*(y-10)=120這一項而已。
2.
The ratio, by volume, of soap to alcohol to water in a certain solution is
2:50:100. The solution will be altered so that the ratio of soap to alcohol
is doubled while the ratio of soap to water is halved.
If the altered solution will contain 100 cubic centimeters of alcohol, how
many cubic centimeters of water will it contain?
Ans. 800
這題我不懂的是，為什麼
"ratio of soap to water is 2:100 if it is halved it us 4:400"(網路上找的解答)
?
3.
The arithmetic mean and standard deviation of a certain normal distribution
are 13.5 and 1.5, respectively. What value is exactly 2 standard deviations
less than the mean?
Ans. 10.5
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 59.105.166.113
討論串 (同標題文章)