19. Arrangement of shoes in A.P: Case study questions.

Veena's brother starts a new shoe store. To display the shoes, he keeps 10 pairs of shoes in the first row, 15 pairs of shoes in the second row and 20 pairs in the third row and so on.

 

 

According to the above details answer the following questions.

 

i) Find the number of shoes in the 27$th$ row

 

ii) The total number of pair of shoes in 6$th$ and 14$th$ row is

 

iii) The difference of pairs of shoes in 18$th$ row and 10$th$ row is

 

iv) Consider, on a next day he keeps $x$ number of shoes in the 21$th$ row, then the value of $x =$