which are 7 times as much as the sum of its two didits.是神马意思啊?_数学解答

which are 7 times as much as the sum of its two didits.是神马意思啊?

人气：385 ℃　时间：2020-05-28 20:33:23

解答

是不是这个意思：
一个两位数,它的值等于自身两位数字之和的7倍.这是什么数?
设十位数为x,个位数为y.
(x + y)*7 = x*10 + y => x = 2y
答案有：21,42,63,84