Exercise 5.2

Complete the following pattern:
$\mathrm{AB}, \mathrm{DEF}, \mathrm{HIJK},\_\_\_\_\_, \mathrm{STUVWX}$

Complete the following pattern:

$20, 19, 17, \boxed{}, 10, 5$

Observe the pattern and find the word by hiding the numbers 

$1H2O3W 4A5R6E 7Y809U$?

Arrange the following from the eldest to the youngest. What do you get?

Observe the geometrical pattern and write down the number of sticks used in each of the iterative pattern.

Observe the geometrical pattern and draw the next figure in the pattern also find the total number of sticks used in it

Find HCF of $28$, $35$, $42$by Euclid's game.

Consider the Postal Index Number (PIN) written on the letters as follows:$604506; 604516; 604560; 604506; 604516; 604516; 604560; 604516; 604505; 604470; 604515; 604520;604303; 604509; 604470.$ How the letters can be sorted as per Postal Index Numbers?