Question

একটি গাছের উচ্চতা প্রতি বছর বৃদ্ধি পায় গাছটির বর্তমান উচ্চতা 28.8মিটার 2 বছর আগে গাছটির উচ্চতা কত ছিল?​

Answer 1

Correct Question:

The height of the tree increases at a rate of 20% every year. If the current height of the tree is 28.8 m. What was the height of the tree 2 years ago?

Given:

The height of the tree increases at a rate of 20% every year

The current height of the tree is 28.8 m

To find:

The height of the tree 2 years ago

Solution:

Let "h" meter represent the height of the tree 2 years ago

The current height of the tree, h' = 28.8 m

The rate of growth of the tree every year, r = 20%

The time period, n = 2 years

We have the formula as,  

$\boxed{\bold{Present \:height (h') = h[1 + \frac{r}{100} ]^n}}$

Now, by substituting the given values in the above formula,  we get

$28.8 = h [1 + \frac{20}{100} ]^2$

$\implies 28.8 = h [\frac{120}{100} ]^2$

$\implies h = 28.8 \times \frac{100}{120}\times \frac{100}{120}$

$\implies h = 28.8 \times \frac{10}{12}\times \frac{10}{12}$

$\implies h = \frac{2880}{144}$

$\implies \bold{h = 20\:m}$

Thus, the height of the tree 2 years ago was → 20 m.

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