题目

one iron thread was used up for a fragment adding one meter equals to the half the original length in the first time;and the remaining has been used up again for another fragment minusing one meter equals to the half of the remaining length ,what is the original length of this rion thread?
2)there is a four -digit number x.A two-digit number of the figures on x`single-digit and tenth-digit is 4 larger than 5 times of another two-digit number composed of the figures on x`s hundredth-digit and on its thousandth-digit,if the locations of “a two-digit number”and “another two-digit number”and exchanged,the newly-got four-digit number is 7920 larger than the original four-digit number,question ：what`s the original four-digit number

提问时间：2021-04-12

答案

第一个问题是问：一根铁丝第一次被用掉的长度加1米就是原长的一半,第二次将剩下的都用掉,而剩下的长度减去1米就是剩下的一半.问,铁丝原来有多长?
剩下的长度减去1米就是剩下的一半,说明剩下的就是2米,那么设原长为x米,则由第一次的条件,可以列式：（x-2）+1=1/2×x,算得x=2米.
感觉题目有点不对头,这样算来的话,第一次相当于没有用铁丝...
第二题题意：有一个四位数x,它的个位和十位组成的两位数比百位和千位组成的两位数的5倍还大4,如果将这两个两位数对调位置,则形成的新的四位数比原来大7920,问：原来的四位数x是多少?
答：1999
式子不好输上来,但是答案我验证过了,绝对正确!