问两道og的ds题目，请大神赐教

mlvince · 发表于 2011-3-5 22:41:13

这两道看了解释也不是很明白。。各位帮忙
AT total of 60000 was invested for one year. Part of this amount earned simple annual interest at the rate of x percent per year, and at the rest eared simple annual interest at the rate of y percent per year. If the total interest earned by the $60000 for that year was $4080, what is the value of x?
(1)x=3y/4
(2)The ratio of the amount that eared interest at the rate of x percent per year to the amount that earned interest at the rate of y percent per year was 3 to 2.

A school administrator will assign each student in a group of n students to one of m classrooms. If 3<m<13<n, is it possible to assign each of the n students to one of m classroom so that each classroom has the same number of students assigned to it?
(1)it is possible to assign each of 3n students to one of m classroom has the same number of students assigned to it.
(2)it is possible to assign each of 13n students to one of m classroom has the same number of students assigned to it.

顺便问下有道题目中这句 the range of the seven remainder is 6是什么意思？

mlvince · 发表于 2011-3-6 09:50:23

sdcar2010 · 发表于 2011-3-6 12:23:31

AT total of 60000 was invested for one year. Part of this amount earned simple annual interest at the rate of x percent per year, and at the rest eared simple annual interest at the rate of y percent per year. If the total interest earned by the $60000 for that year was $4080, what is the value of x?
(1)x=3y/4
(2)The ratio of the amount that eared interest at the rate of x percent per year to the amount that earned interest at the rate of y percent per year was 3 to 2.

principal a 60000-a
interest rate x y
interest a*x (60000-a)*y

a*x + (60000-a)*y = 4080. Basically we have three unknowns (a, x, and y) and only one equation. We need two more equations to solve a, x and y.

1) x=3y/4
2) a/(60000-1) = 3/2

CCCCCCCCCCC

sdcar2010 · 发表于 2011-3-6 12:32:59

A school administrator will assign each student in a group of n students to one of m classrooms. If 3<m<13<n, is it possible to assign each of the n students to one of m classroom so that each classroom has the same number of students assigned to it?
(1)it is possible to assign each of 3n students to one of m classroom has the same number of students assigned to it.
(2)it is possible to assign each of 13n students to one of m classroom has the same number of students assigned to it.

Basically it asks you if m is a factor of n, or if n = m*k.

1) 3n = m*k1 or n = (m*k1)/3. Since m could be 6 or 9 or 12, k1 is not required to be a multiple of 3. Therefore, this condition is not sufficient to tell if n = m*k.
2) 13n = m*k2 or n = (m*k2) /13. Since m could not be 13 or its multiples, k2 has to be a multiple of 13. Therefore, n = m*(k2/13) wherein k2/13 is an integer. Sufficient.

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sdcar2010 · 发表于 2011-3-6 12:33:57

the range of the seven remainder is 6

You got seven remainder(s) or numbers. The difference between the biggest and the smallest number is 6.

心诚则灵的MM · 发表于 2011-3-6 18:35:46

A school administrator will assign each student in a group of n students to one of m classrooms. If 3<m<13<n, is it possible to assign each of the n students to one of m classroom so that each classroom has the same number of students assigned to it?
(1)it is possible to assign each of 3n students to one of m classroom has the same number of students assigned to it.
(2)it is possible to assign each of 13n students to one of m classroom has the same number of students assigned to it.

Basically it asks you if m is a factor of n, or if n = m*k.

1) 3n = m*k1 or n = (m*k1)/3. Since m could be 6 or 9 or 12, k1 is not required to be a multiple of 3. Therefore, this condition is not sufficient to tell if n = m*k.
2) 13n = m*k2 or n = (m*k2) /13. Since m could not be 13 or its multiples, k2 has to be a multiple of 13. Therefore, n = m*(k2/13) wherein k2/13 is an integer. Sufficient.

BBBBBBBBBBBBb

-- by 会员 sdcar2010 (2011/3/6 12:32:59)

为什么从K1，k2是否能分别被3和13整除，而作出判断？没搞明白。。。

sdcar2010 · 发表于 2011-3-6 21:06:11

First, n is an integer, meaning in condition 1) (m*k1)/3 is also an integer. To make (m*k1)/3 an integer, 3 has to be a factor of m and/or k1. If 3 is a factor of m, then m itself might not be a factor of n.

gdnz0831 · 发表于 2011-3-6 22:02:49

I agree "C"

Zhongtianwu · 发表于 2011-3-8 19:00:45

谢谢sdcar, 解释得很清晰，致礼！

问两道og的ds题目，请大神赐教

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