紧急求助两道prep数学

pp0614 · 发表于 2010-8-9 09:09:00

Q1

70，75，80，85，90，105，105，130，130，130
The list shown consisted of the times, in seconds, that it took each of 10 schoolchildren to run a distance of 400 meters.If the standard deviation of the 10 running times is 22.4 seconds, rounded to the nearest tenth of a second, how many of the 10 running times are more than 1 standard deviation below the mean of the 10 running times?

A. One
B. Two
C. Three
D. Four
E. Five

I'm confused about the meaning of the question: what does that more than 1 standard deviation below the mean of the 10 running times mean? And please tell me tell me the approach to solve this problem.

Q2

+	x	y	z
4	1	-5	m
e	7	n	10
f	2	-4	5

In the addition table shown above, what is the value of m+n?
( 实际的题最左边一栏和最上面栏与其余部分是线分开的，其余部分间无线；原图见附件）

I can't understand this question and don't know how to solve it.

谢谢各位大侠帮助了！！

fengshou · 发表于 2010-8-9 12:29:24

1:
Standard deviation你可以去查金山词霸

首先算出10个数的平均数，然后减去22。4就是1个standard deviation below the mean的数字小于这个数字的都是你要的你就数这种数字的个数就行了我得出的是B

2:
m+n=(z+e)+(4+y)=10-5=5

紧急求助两道prep数学

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