提问几道GRE数学题

题目

提问几道GRE数学题
P48
A number between 5 and 10与A number between 8 and 14比大小 答案是不确定
The number of different positive divisors of 12与the number of different positive divisors of 50比大小
P49
x,y,z are positive integers,and z>x>y.The remainder when z is divided by x与The remainder when z is divided by y比大小 答案是不确定
P43
A purchase plan for a stereo receiver requires 20 percent of the total cost as a down payment and monthly payments of $30.The total cost of the stereo receiver与$450比大小 答案是不确定
P40
In a certain two-digit number,the units' digit is twice the tens' digit.The tens' digit与5比大小 答案是后者大

答案

A number between 5 and 10是一个5-10之间的数,A number between 8 and 14是一个8-14之间的数,所以大小关系不确定,可能前者大,也可能后者大,或相等
The number of different positive divisors of 12是12的正因数个数,有1,2,3,4,6,12共6个
the number of different positive divisors of 50是50的正因数个数,有1,2,5,10,25,50共6个
所以相等
x,y,z are positive integers,and z>x>y.
The remainder when z is divided by x指z除以x的余数
The remainder when z is divided by y指z除以y的余数
这是不确定的,举例来说吧,
如 10>9>8,这时10除以9的余数比10除以8的余数小
10>8>3,这时10除以8的余数则比10除以3的余数大
10>9>3,这时两者相等
A purchase plan for a stereo receiver requires 20 percent of the total cost as a down payment and monthly payments of $30.
题目没说要一共付几个月,所以无法确定总价,也就无法与450比大小了
In a certain two-digit number,the units' digit is twice the tens' digit.
一个两位数的个位数字是十位数字的两倍,那么十位数字肯定比5小,否则个位数字就大于或等于10了.