2,000 tk
Let, the principal be Tk. x
so, Amount of compound interest = x $(1+\frac{8}{100})^{2}$-x = x$(\frac{100+8}{100})^{2}$-x = x $(\frac{108}{100})^{2}$-x = x$(\frac{27}{25})^{2}$-x
= x$\times \frac{729}{625}-x=\frac{729x}{625}-x=\frac{729x-625x}{625}=\frac{104x}{625}$tk
And amount of simple interest = $\frac{104x}{625}-\frac{4x}{25}$ =12.80
=> $\frac{104x-100x}{625}$ = 12.80
=> 4x = 625×12.80
=> x= $\frac{625×12.80}{4}$ = 625×3.20
so, x = 2,000 tk
3.5 minutes
Sally takes 1 minute to make $\frac{40}{2}$ = 20 pancakes.
Sally makes 20 pancakes in 1 minute.
Sally makes 30 pancakes in =$\frac{30×1}{20}$= 1.5 minute.
Remaining (15O -30) = 120 pancakes are made by both of them.
Now. Jaya and Sally takes 1 minute to make = 40 + 20 = 60 pancakes.
That means. 1 pancake is made by them in = $\frac{1}{60}$ minutes
120 pancake is made by them in =$\frac{1×120}{60}$ = 2 minutes
Total time taken by them to make 150 pancakes is = 2 min + 1.5 min = 3.5 minutes.
