1. Find the smallest number which should be added to the largest 7-digit number to make it exactly divisible by 23.

2. Mark three non-collinear points X, Y, Z. Draw lines through these points taking two at a time. Name the lines. How many such different lines can be drawn?

3. How many degrees are there in 4/5 of a right angle?

4. Find the greatest number which exactly divides 134, 178, and 262.

5. Find the greatest 4-digit number which is exactly divisible by 19, 29, and 39.

6. Find the least 6-digit number which is exactly divisible by 12, 36, and 48.

7. Find the greatest 5-digit number which is exactly divisible by 7, 8, 9, and 11.

8. Find the least number, which when divided by 10, 20, and 40 leaves a remainder 5.

9. Find the greatest number which when divides 1179 and 1498 leaves a remainder of 3 and 2 respectively.

10. A rectangular room is \(2400 \text{ cm}\) long and \(1800 \text{ cm}\) broad. It is to be paved with square tiles of the same size. Find the least possible number of such tiles.

11. Subtract the sum of -185 and 131 from the sum of 510 and -615.

12. Add the difference between -155 and 147 to the sum of 315 and -705.

13. Subtract the sum of -249 and 159 from the sum of 529 and -635.

14. If you add the sum of -205 and 139 to a number, you get 455. What is that number?

15. Subtract the sum of -295 and 141 from the sum of 317 and -641.

16. ? + 11 = 23.

17. ? + -14 = 22.

18. ? + 10 = 35.

19. ? + -6 = 13.

20. ? + 11 = 27.