Question

wants to send a letter to Peter, who lives on Tesla
John doesn't remember the house number.
ver, he knows that it has 4 digits, it is a multiple of 5
and that the last digit is 0. What is the minimum number
ers that John has to send to be sure that Peter receives his letter?​

Answer 1

John has to send a total number of 127 letters to peter to make sure that he receives this letter.

Explanation:

As the last digit of the house number = 10  

Now the house number is divided by 10 which also meets the condition that it should be divisible by digit 5.

From 1000 to 999, we have four digits.  

So the numbers that can be divided from 7 and 10 are from  (1000/70 (Which is 14 + 2/7) - 2/7)×70 + 70 = 1050 to (9999/70 (Which is 142 + 59/70)- 59/70)×70= 9940

This means 142-15 = 127

hence the number of the letters is 127