Unicornrabbit

1. The numbers in which 3 occurs only once. This means that 3 is one of the digits and the remaining two digits will be any of the other 9 digits

You have 1*9*9 = 81 such numbers. However, 3 could appear as the first or the second or the third digit. Therefore, there will be 3*81 = 243 numbers (1-digit, 2-digits and 3- digits) in which 3 will appear only once.

2. The numbers in which 3 will appear twice. In these numbers, one of the digits is not 3 and it can be any of the 9 digits.

There will be 9 such numbers. However, this digit which is not 3 can appear in the first or second or the third place. So there are 3 * 9 = 27 such numbers.

In each of these 27 numbers, the digit 3 is written twice. Therefore, 3 is written 54 times.

3. The number in which 3 appears thrice - 333 - 1 number. 3 is written thrice in it.

Therefore, the total number of times the digit 3 is written between 1 and 999 is 243 + 54 + 3 = 300

Thank you!

I understand now. Thank you.

Even just an approach to my question? Anyone?

First, we should assign variables.

Sandra’s Age = X + 18

Paolo’s Age = X

In 13 years, they will be:

(X + 18) + 13 = 2(x + 13)

X + 18 + 13 = 2x + 26

X + 31 = 2x + 26

X – 2x = 26 - 31

-x/-1 = -5/-1

X = 5

Therefore, Sandra is now:

Sandra’s Age = 5 + 18 = 23

Sandra is now 23 years old.

Checking their age:

23 (Sandra) – 5 (Paolo) = 18

If z>=0,
2+z > 1 -- z > -1
2-z <= -1 -- z >= 3

If z<0,
2-z > 1 -- z < 1
2+z <= -1 -- z <= -3

If you graph on a number line, you will find your answer. Check a few values to make sure they work, especially at the boundaries.

We can make a variable a to be his age.

36+a = 2.5a
36 = 1.5a
24= a

proof: 2.5*24 = 60 = 24+36

Does that help?

Oh i looked it up sounds cool