Fifth grade primary school mathematics interesting questions, to process, seek solutions If you add 5 to the number, the two numbers will be the same. Find the two digits Need a detailed answer process

Fifth grade primary school mathematics interesting questions, to process, seek solutions If you add 5 to the number, the two numbers will be the same. Find the two digits Need a detailed answer process

The number of one digit is three times that of ten digit. There are three digits, 13, 26 and 39 respectively
If you add 5 to this number, the two numbers will be the same, only 39 + 5 = 44
So the double-digit number is 39

Interesting problems in Mathematics

1. There are two incense distributed unevenly. The burning time of incense is one hour. What method can you use to determine a period of 15 minutes? A: light up two incense at the same time, the first incense is burning at both ends, and the other incense is burning at only one end. When the first incense is burned (this is 3 / 4 of the total length), turn the second incense to the other

For a four digit number, the first number on the left is 7. If the number is adjusted to the last digit, the number will be reduced by 864. Find out the four digit number (solution to the equation)

Let the size of this four digit number be 7000 + X, then after changing the order, according to "the number 7 is transferred to the last digit, the rest of the order remains unchanged, then this number will be reduced by 864", the equation can be obtained as follows: 7000 + x-864 = 10x + 7, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & 9x = 6129, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; X = 681; so the four digit number is 7000 + 681 = 7681. A: the four digit number is 7681