一道英文数学题=

题目

一道英文数学题=
There are five numbers.Their average is nine.If we change one number to one,and another number to two,the average becomes eight.If we rechange these two numbers:one number to two times as many as its original value,and the other to four times as its original value,the average of the five numbers will become thirteen.Which two numbers have been changed?

答案

设There are five numbers为 A B C D E
则 A+B+C+D+E=5*9=45
1+2+C+D+E=5*8=40
2A+4B+C+D+E=13*5=65
解得 A=2
B=6
即 6 and 2 two numbers have been changed