Question

how to solve this question
A tree increase annually by 1/5 th of its height.what is the change in height in last 2 years.if it stands 36cm high today?
can u explain logically, don't use compound interest formula..

Answer 1

Tne tree increases by 1/5 th of its height annually. That is by 20%.
For eg if it was 1 m at a given time, then a year later it would be 1 + 20% of 1m = 1.2 m
Now what I understand from your question is that its final height is 36 cm and we have to find its height 2 years ago.
Let X be the height of the tree 2 years ago.
Therefore the height of the tree 1 year ago would be X + 20% of X = 6×X/5.
Therefore the height of the tree in terms of X would today be
》6×X/5 + 20% of 6×X/5 =36 (the data given in the question)
》 6X/5 + 6X/25 = 36 cm
》36X/25 = 36 cm.
》 X = 25 cm.

Hence the tree was 25 cm tall two years ago.
Hence the change in height in two years is:
》 36 - 25
》 11cm

Hence the answer is 11 cm

Answer 2

if tree grows 1/5th part of its real height per year then the simple logic is that subtract 1/5 from from the real height of the tree thai is 36= it is last 1 year height of tree

to findout the last 2 years height of tree then subtract 1/5 from the height of of last 1 year