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.写过程(7题)(英文的)1.X的平方+Y的平方+Z的平方=390,X,Y,Z都是正整数请问X+Y+Z=多少Questi
题目内容：
.写过程(7题)(英文的)
1.X的平方+Y的平方+Z的平方=390,X,Y,Z都是正整数请问X+Y+Z=多少
Question 2
A carpenter has a long rod of length 4m83cm.He needs to cut this rod into lengths of 161cm,23cm and 7cm so that he would get at least one rod of each length and have nothing left over.After a while,the carpenter managed to solve this problem.How many rods of each length did he get?Find all possible solutions.
Question 3
Points A and B are on the banks of a river.It takes a motorbank 1 hour to go down-stream from A to B and 1.5 hours up-stream from B to A.How long would it take the mtorboat to go from C to D and back,if C and D are on the shores of a still lake and C to D is the same distane as A to
Question 4
The executive director of the "Smart Solutions" company wishes to employ 9 new staff members.There are 14 applicants:4 mathematicians and 10 accountants.In how many ways can the executive director select 9 people if he wants to employ at least one mathematician?
Question 5
Show that (29 times 20^99) + (71 times 56^64) + (24 times 37^55) is divisible by 19.^means power ex 2^2 two squared 2^3 two cubed * means times
Question 6
For the Pan Australian Games the three states at the top of the medals table (Victoria,S.A.and W.A) had won a total of 186 medals.Victoria has won the most gold medals and SA had as many gold medals as bronze medals.Victoria and SA won the same number of silver medals.WA had two more silver medals than bronze medals and their gold medals numbered one more than Victoria's bronze medals.Victoria had as many gold medals as the bronze medals of SA and WA combined and this number was also three quarters the total number of medals won by SA.The number of gold medals won by the three states was one less than the total number of medals won by Victoria.How many of each medal did each state win?
Question 7
A number is written on a whiteboard.Jim writes 221 to the right of this number thus obtaining a new number which turns out to be a multiple of the original one.What is the original number?Find all possible solutions
食饭睡觉打东东 你真是天才..拜托你告诉我一下第一题那3个数字怎么得出来的好吗?能知道你的QQ或者MSN吗?我实在懒的用百度这东西优质解答
Q1：X+Y+Z=26（x=19,y=5,z=2）
Q2：因为483=3×161=3×7×23,且每个尺寸的木条都要有（至少一根）.
所以,只有一种情况：161cm的一根,23cm的7根,7cm的23根.
Q3：设摩托艇的静水速度为v,水流速度为x,可得方程
v+x=1.5(v-x) 两点距离相等
解得v=5x.
再设从C到D的时间为T,则
v+x=vT 距离相等
把v=5x代入,解得
T=1.2Hs
Q4：至少一个人是数学家,也就是先从4个数学家里面挑一个 C 4 1
然后剩下13个里面任意挑8个填补剩下的位置 C 13 8
（C 4 1 表示组合数,由于这里编辑不了,所以只能这样写出.）
两项相乘4×13×12×11×10×9=617760 种挑法
Q7：因为在原数字右边加了221 以后 那个数字是原数字的倍数,可设原数字为X,得方程：1000X+221=nX n=1,2,3,...
解方程得X=-221/1000-n
因为X应为正整数,所以分母应为221的倍数的负数.
将221分解因式,为221=13×17.
同时,1及221的倍数也为221.
所以,n可能为1001,1013,1017,1221,
分别可得出X为221,17,13,1.
（其他问题可以在线问我,有些数学符号在这里打不出来）
楼上的,请问Q5 你为什么写个15出来呀?
1.X的平方+Y的平方+Z的平方=390,X,Y,Z都是正整数请问X+Y+Z=多少
Question 2
A carpenter has a long rod of length 4m83cm.He needs to cut this rod into lengths of 161cm,23cm and 7cm so that he would get at least one rod of each length and have nothing left over.After a while,the carpenter managed to solve this problem.How many rods of each length did he get?Find all possible solutions.
Question 3
Points A and B are on the banks of a river.It takes a motorbank 1 hour to go down-stream from A to B and 1.5 hours up-stream from B to A.How long would it take the mtorboat to go from C to D and back,if C and D are on the shores of a still lake and C to D is the same distane as A to
Question 4
The executive director of the "Smart Solutions" company wishes to employ 9 new staff members.There are 14 applicants:4 mathematicians and 10 accountants.In how many ways can the executive director select 9 people if he wants to employ at least one mathematician?
Question 5
Show that (29 times 20^99) + (71 times 56^64) + (24 times 37^55) is divisible by 19.^means power ex 2^2 two squared 2^3 two cubed * means times
Question 6
For the Pan Australian Games the three states at the top of the medals table (Victoria,S.A.and W.A) had won a total of 186 medals.Victoria has won the most gold medals and SA had as many gold medals as bronze medals.Victoria and SA won the same number of silver medals.WA had two more silver medals than bronze medals and their gold medals numbered one more than Victoria's bronze medals.Victoria had as many gold medals as the bronze medals of SA and WA combined and this number was also three quarters the total number of medals won by SA.The number of gold medals won by the three states was one less than the total number of medals won by Victoria.How many of each medal did each state win?
Question 7
A number is written on a whiteboard.Jim writes 221 to the right of this number thus obtaining a new number which turns out to be a multiple of the original one.What is the original number?Find all possible solutions
食饭睡觉打东东 你真是天才..拜托你告诉我一下第一题那3个数字怎么得出来的好吗?能知道你的QQ或者MSN吗?我实在懒的用百度这东西
优质解答
Q2：因为483=3×161=3×7×23,且每个尺寸的木条都要有（至少一根）.
所以,只有一种情况：161cm的一根,23cm的7根,7cm的23根.
Q3：设摩托艇的静水速度为v,水流速度为x,可得方程
v+x=1.5(v-x) 两点距离相等
解得v=5x.
再设从C到D的时间为T,则
v+x=vT 距离相等
把v=5x代入,解得
T=1.2Hs
Q4：至少一个人是数学家,也就是先从4个数学家里面挑一个 C 4 1
然后剩下13个里面任意挑8个填补剩下的位置 C 13 8
（C 4 1 表示组合数,由于这里编辑不了,所以只能这样写出.）
两项相乘4×13×12×11×10×9=617760 种挑法
Q7：因为在原数字右边加了221 以后 那个数字是原数字的倍数,可设原数字为X,得方程：1000X+221=nX n=1,2,3,...
解方程得X=-221/1000-n
因为X应为正整数,所以分母应为221的倍数的负数.
将221分解因式,为221=13×17.
同时,1及221的倍数也为221.
所以,n可能为1001,1013,1017,1221,
分别可得出X为221,17,13,1.
（其他问题可以在线问我,有些数学符号在这里打不出来）
楼上的,请问Q5 你为什么写个15出来呀?
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