Question

ARITHMETIC PROGRESSIONS CLASS 10


In a garden there are 30 mango trees in the first row, 27 in the second row, 24 in the third row and so on .There are 6 trees in the last row. How many rows are there of mango trees.

Answer 1

Answer:

30,27,24,21,18,15 =135

Answer 2

a1=30.

a2=27

Therefore d= a2 - a1

=27-30

= -3

an = 6

an = a+(n-1)d

6. = 30+(n-1)-3

6. = 30 - 3n +3

6 = 33 - 3n

6-33 = -3n

-27. = -3n

-27/-3 = n

+9. =n

Therefore there are 9 rows of mango trees.

Hope it helps you.