If you multiply 3 by 3 100 times (i.e. 3 x 3 x 3 x 3... x3), what is the unit digit of the product?

If you take the number X, add 7, multiply by 7, subtract 7, then divide by 7, the result is 7. What is X?

If you take the number Y, subtract 6, divide by 2, add 10, then multiply by 2, the result is 100. What is Y?

How many multiples of 3 sit between 10-100?

How many multiples of 4 sit between 10-100?

Adam writes 1, 2, 3, 4, ... 100 on 100 index cards to play a game with Desmond. How many times does he write "1" ?

Neal is practicing additions. He accidentally takes the 1 on unit digit as 7, and the 6 on tens digit as 9. If his answer is 75, what's the correct answer?

Adam is amused by the following facts. He wants to know if the pattern will continue. Can you help him find out the pattern?

```
1x8+1=9
12x8+2=98
123x8+3=987
1234x8+4=9876
12345x8+5=98765
```

1） 1

2）1

3）86

4）30

5）22

6）20

7）51

8）123456X8+6=987654